While I also recommend upgrading to v3, there are some plugins which have not yet been updated to work with 3.0, which is why I also keep my 2.0.0.14-2.0.0.15.
Many extensions can be easily 'max version bumped'. (that is, made to work with newer versions they were originally intended for.)
Download the .xpi. and open it in the archive manager and extract and edit install.rdf, it's a standard text file. There you'll see the max version defined. Make it something bigger. Then add the modified install.rdf back to the xpi archive. Finally drag & drop the .xpi onto Firefox window.
Note, doing this might break your profile, so take any precautions you want.
As much as I would love to upgrade to v3, doing so would break access to my college website. The site has specifically mentioned FF3 as NOT being compatible with the site - specifically, with the site text editors (tool buttons do not show up, html embedded in the text editor's text is not parsed, etc.