As a part of my Google Summer of Code project in 2008, I wrote an extension to synchronize contacts between Google and an address book in Thunderbird. As a result, I know the basics of making an extension and have some familiarity with the code for Thunderbird (and the core of Firefox).
Below is a list of the extensions I have written. See the Blog link above for news and the Forum & Wiki links for support
- gContactSync - Synchronizes contacts from Google with address books in Thunderbird.
Contact Photos - Displays contact photos and Gravatars in the message header
- openCRX - Imports contacts from and exports contacts to an openCRX server.
- File Type Selector - Allows one to change the default file type for saving e-mail messages.