With Firefox 3 RC1 just around the corner, Basil Hashem has just announced the availability of the the "3.0" and "3.0.*" Firefox compatible versions at AMO.
This means that add-on developers who have tested with Firefox 3 RC1 can offer those add-ons as being compatible with the final version of Firefox 3.
If you're an add-on developer and you're already compatible, you can flip that switch now. If you're not yet compatible because you've been waiting for the final release, now's the time to dive in.