Hey guys,
I figured I'd share this little tidbit of info I found on a mozilla forum. If you're looking to install the Spoofstick plug-in on Firefox 2.0, the default .xpi won't install it (says FF 2.0 is not supported or something yadda yadda).

This workaround will fix that issue.
- download the spoofstick-firefox.xpi (the file itself)
- open the .xpi with Winzip (should be a total of 3 files)
- find the file called install.rdf
- open install.rdf with Notepad
- look for this line: <em:maxVersion>1.6a2</em:maxVersion>
- change 1.6a2 (or whatever the number is) to 2.0 or higher
- save and close it (select "yes" when it asks to update the zip archive)
- install the plug-in

Here's a site where you can download the file (it won't auto-install it)

p.s. - Don't thank me, thank JC (the guy who posted this on the mozilla forum)