Yes, I once used http://www.hotscripts.com/listing/tr-newsportal/
More here: http://www.hotscripts.com/category/php/scripts-programs/usenet-gateway/
It's an interesting subject for me also, but I just can't find much about it. I made me think of the interface Stephane Marchau had written for the free usenet access on http://www.mes-news.com, based on some serious thinking on how to make a very decent interface, but it's down now, and it seems he never released publicly, have no idea how to contact him.
I just saw that Dnews has a web interface DNewsWeb and there's also SurgeNews, but I had no idea until now Dnews was a commercial software ...
TR-NewsPortal doesn't look like it's been updated in about 5 years. It was also a fork of another product called NewsPortal, which is still being actively maintained (last release was just 2 months ago). I've been playing around a little with NewsPortal, it works well, but it's a far cry from Google Groups. :) Might be a good starting point though.
Posted by Dave Miller at July 13, 2009 8:11 PMHi, I already posted a comment whichi didn't appear with link to the NNTP - web forum gateway of vBulletin :
http://www.vbadvanced.com/forum/showthread.php?t=23630
http://www.vbulletin.org/forum/showthread.php?t=92588
According to what I see here
http://www.arkadia.com/fra/forums/f20/ which is a copy of news://fr.misc.droit.immobilier it seems to work quite well.