Gina at lifehacker has compiled and written a great little extension for gmail that you can get from her site.
Lifehacker Code Update: Better Gmail Firefox extension version 0.7 now available – Lifehacker
To me so far the best part about this Firefox extension is the fact that all of those mailto: links on pages can now become gmail email links so that I can have work stuff for work and use my gmail to email much more efficiently. How does this work? Well if you have the extension installed you will see a little gmail envelope beside any links to that are email links on a page. Click on the gmail icon and it will being up a new tab with the compose email window for gmail and the email address already populated in the to: field
