Enhances the new Gmail interface with Greasemonkey user scripts. Only compatible with the NEW Gmail interface.Not sure whether you need Better Gmail or Better Gmail 2?

Better Gmail 2 Firefox extension

Version: 0.3.3
Updated: February 14, 2008 (because I love you)
Released: November 8, 2007
Creator: Gina Trapani, using scripts by Mihai Parparita and others, compiled using Anthony Lieuallen’s Greasemonkey Compiler.

Installation: Click the Better Gmail 2 download button below in Firefox. A yellow bar will appear across the page that reads “Firefox prevented this site (lifehacker.com) from asking you to install software on your computer.” Click the “Edit Options” button and allow lifehacker.com to ask you. Then, click on the link again. Press the Install button in the dialog box, and restart Firefox.

Can be downloaded at Firefox Extensions:

 https://addons.mozilla.org/en-US/firefox/addon/6076