I'm always trying extensions and seeing how long I can cope with them. To date, I've really only stuck with one for longer than a few months and that's the Link Visitor extension which allows you to modify the visited/unvisited state for links.
I find this extension comes in really handy for keeping track of which pages, articles, bugs, etc. that I've read. For example, if I was just looking at a bug a few days ago and I do a search to find it again, it'll stick out as visited in the buglist. That only works until you've read as many bugs as I have. Now, I just mark as unvisited any bugs that I'm not interested in keeping an eye on right there on the bug page. It's also useful at sites like The Register where they keep loads of links to other articles all on the same page and make updates really regularly. I can mark the whole page as visited when I've read all I care to and the next time I visit the page, only the new articles are linked as unread.
Next on my list for almost holding on to is Linky which I find myself needing in bursts and then not wanting to have cluttering my menu for a while. Being able to uninstall or disable extensions sure is nice.
Other than those two, I haven't really held onto any Firefox extensions for very long. For the most part, Firefox does exactly what I need it to do. It really is a quite powerful browser "out of the box."
I mentioned a couple of weeks ago the SpellBound extension and I'm still holding on to that one but the pain of having to do a fresh install with every new daily build is getting to be a bit much so I don't know how much longer I'll keep it. It's nice to have but I rarely use it and it's a pain to repeatedly install.
I think I forgot to mention another extension that I installed at that time and that I'm pretty sure I'll hold onto for some time and that's the MiniT (drag+indicator) extension which is a very clean, very well done, nearly perfect extension. It does what it's supposed to do, does nothing else, it's out of your way when you don't need it, and I haven't found any bugs in it yet. If you want to drag and drop reorder your tabs and you don't want to deal with extensions that break the Web (like TBE) I highly recommend this one. (note: the drop indicator icon is one I made and dropped in. I'm constantly replacing icons in extensions because so few fit in with the default theme.)

Today, I installed two more extensions that I can see holding onto for a while, the Translate and TinyURL Creator extensions. Both are fairly clean and seem to work just fine. I've made my own icons because the ones I find in extensions usually don't fit well with the default theme, but other than that, they're functioning quite nicely.
If you know of good extensions, let me know. I'm always up for trying a new one.
update Paul, the Translate developer. has a new icon that's much nicer
and I've scaled that down a bit to better fit in with my default Firefox theme
. This really is an area where we need to come up with a better solution. I'd recommend that Firefox themes include a few "generic" icons like the document and maybe some arrows and other shapes, that extensions can overlay with their image. That way, for example, Paul could build his icon by just overlaying the "EN" on top of one the generic icon. It would lead to more seamless extension integration, I think.
There are only a few that I've kept around also.
AiO [link] I can't like without mouse gestures anymore.
Download Status Bar [link] I prefer this graphical representation better than the Download Window
RSS Reader Panel(which I guess is just sage now) [link] I have an RSS addiction.
&
Statusbar Clock [link] In windows I keep my task bar minimized so it's nice to have a clock visible.
That's a cool icon for the drop indicator, a lot better than the one that comes with the extension.
Is there a chance you'll submit it (and your other icons) to the extension developers so that perhaps they'll use the better icons?
Posted by: Jason on July 31, 2004 05:42 PMI have been a supporter of Optimoz gestures for 2 years now...
I have 2 friends that worship TabBrowser Extensions... Although I currently see it as a bit invasive.
Larf
Posted by: larfnarf on July 31, 2004 05:43 PMHi Asa,
I've noticed that you mentioned that you've designed a new icon for my extension (Translate). I'd be extremely curious to see how yours differs from my mine, would you mind sending me a screenshot? Don't worry, I don't intend on ripping it, but rather get a clue as to which direction I should be heading.
As you are probably already aware, I'm no designer.
Posted by: Paul Grave on July 31, 2004 05:53 PMThis comment comes under the category of "spoiling Asa's perception of perfection":
Open the sidebar, drag a tab, et voila - bug :)
You absolutely HAVE to try Linkification. If you've ever come across a URL or email address that wasn't HTMLified, and you had to click, drag, copy, go to your address bar, paste and hit return, then you'll love it. It automatically converts any URL and any email address (along with special protocols like FTP and eDonkey links) into clickable links wich work exactly as if they had proper html target information.
By default it also highlights all links with a special backgroun colour, but you can turn this off so "linkified" links look like normal clickies.
- Chris
Damn you Greg! Damn you to hell!! ;-) You are correct. I guess it's a good thing I don't use the sidebar. Too bad. I've been looking for a long time for a simple, bug-free extension and I thought I'd found it. You've ruined my day :)
--Asa
Posted by: Asa Dotzler on July 31, 2004 07:34 PMBugger. So that's what the problem was. I always have the sidebar open, and I was wondering why the indicator was always in the wrong place.
Still, it's a pretty neat extension.
Some extensions that I like:
All-in-One Gestures: Left- previous tab, Right- next tab, Down- Close tab. Can't live without it.
BBCode: I spend a lot of time in forums, so this is a lifesaver.
Adblock: (Obvious)
Tabbrowser Preferences: Like single window, but requested popups still 'pop-up'
NetUsage: Great tool for broadband users with limited downloads: adds a usage meter to the toolbar. [netusage.mozdev.org]
Posted by: Phill Bryant on July 31, 2004 07:42 PMI'd been meaning to write on 2 killer extensions but never had the time. I think I'll do a writeup on those on Monday or Tuesday. I can't believe they haven't been mentioned here yet!
Posted by: Cheah Chu Yeow on July 31, 2004 08:14 PMPaul, I'm no designer either. I just spend a few minutes trying to make something that's a better size than the defaults that most extension makers make and sometimes I try to hack in something that makes it feel more at home on my toolbar like an arrow or highlight or a color or something. If I was going to spend any significant time on an icon for Translate, I think I'd like to have a document-like icon with "EN" on it and the arrow pointing at it. BTW, I posted the quick image I created up in this blog post. It's not worth much because I did it in like 5 minutes mostly to get the size better for my toolbar.
--Asa
Posted by: Asa Dotzler on July 31, 2004 08:50 PMATM got User Agent Switcher, Googlebar, Web Developer, and Google Preview and have been using them for a while.
I'd recommend looking into GooglePreview, it's pretty nifty.
http://ackroyd.de/googlepreview/
Posted by: Cow on August 1, 2004 12:59 AMI can't live without Adblock. It's always the first extension I install.
Hi Asa,
Thanks for the pointers. When it came to the icons sizes, I stuck to the standard 16x16 and 32x32 for no particular reason, are you saying that they can be any size? After reading what you said, I did a quick redesign.
Posted by: Paul Grave on August 1, 2004 06:36 AMPaul, that looks great. When it comes to icon size, you're kinda hosed. See, each theme has it's own icon size. The default theme for Firefox 1.0 will probably stick to roughly the same size it has now, which is 24x24. Icons that are radically different sizes than that look fairly out of place. There's also a pretty simple style that most of the default icons stick to which is a fairly dark border, with a highlight inside of that and a diagonal gradient inside of that (for the basic shapes).
Your new icon has a much better style than the old one and I think it would look great in a somewhat larger theme like Qute. For the default theme, trimming it down a bit further to be closer to that 24x24 would be nice. I grabbed your quick redesign and scaled it down some and it fits in great with my Firefox now. Nice work.
--Asa
Posted by: Asa Dotzler on August 1, 2004 07:47 AMPaul, if you're interested in using this icon, I've created an image with the three states (active, hover, and disabled) and posted it here. That would cover the standard icon size. I'd be happy to try to create the smaller size if you're interested (though maybe not 'till next weekend.)
--Asa
Posted by: Asa Dotzler on August 1, 2004 09:32 AMI know it's been mentioned already here and in many other places. But I think the web developer extension is the perfect extension (for me) I can't imagine being without it now.
There's a neat trick I use with Web Developer which would probably be of use to others. You can fix the display bugs in table-heavy sites like Slashdot by using Web Developer to outline table cells and then un-outline them. It forces the page to re-render and makes it readable.
I also use it to style pages on the fly if they're hard to read. I have a stylesheet saved that makes plain text much more readable
Posted by: Rory Parle on August 1, 2004 10:24 AMHeh. Well, it only took a few minutes so here's a smaller version of the Translator icons (larger ones still here. Paul, if you're interested in using these, feel free. I think they fit fairly well with the Firefox default theme, though they lack the drop shadow of the other icons. Using -moz-image-region, you can specify the three different states use the appropriate piece of each of these two images or you could join the large and small into one image and select with -moz-image-region from that. The default state should be used whenever the button is available for use, the hover state for when the user mouses over the button and the disabled state for when the button shouldn't be available (not sure when that is, maybe with local content loaded, about:blank, images, etc.)
--Asa
Posted by: Asa Dotzler on August 1, 2004 10:26 AMHi, I'm the author of the miniT drag+indicator extension. (which is a mod of Dorando's miniT drag)
Asa, can you send me your drop arrow? I'll gladly replace the diamond with it.
Also, I'm aware of the sidebar bug. I'll fix it in a next release.
Posted by: caio chassot on August 2, 2004 06:33 PMCaio, I've mailed you the little icon I have. If you like it, feel free to use it. I'd be happy to try to style that diamond icon up a bit more to look like the rest of the default firefox theme if you'd prefer that.
I was talking with Ben and Blake today and Ben said that you could fix the sidebar problem by calculating the horizontal offset using the tab containing box's boxObject .x property not the screen or window origin.
If you can take care of that problem, I'll be keeping this extension around permanently :)
--Asa
Posted by: Asa Dotzler on August 2, 2004 08:43 PMHow does TBE break the web? I know it's buggy, but what do you mean?
Posted by: Chris Wood on August 4, 2004 06:12 AM