If you don't know about Thunderbird, then you've been living under a rock. Its a small, lightweight, Email application provided free by the Mozilla foundation. I was looking around for Thunderbird add-ons this evening and found a couple that I found to be a "Must Have" for anyone that uses Thunderbird as their primary email client. I'll list them off in no particular order:

Enigmail - OpenPGP message encryption and authentication for Thunderbird and Seamonkey.

Thunderbird is a pretty great open sourced mail client that is available on multiple platforms and for free. From the beginning its development has been mostly be shadowed by FireFox. The two core developers of Thunderbird have left Mozilla, which is a big blow to the ongoing development of Thunderbird. Will Thunderbird not longer get as many updates or new features? Will development complete stop? Only time will tell.

Unfortunately there is no swiftweasel for debian etch/testing:

I had to browse to the SourceForge project page, and download the appropriate version for my machine, which is a athlon64/32bit.

I just untar'd the file, and ran ./firefox from within the directory and it picked up all my settings and everything. Next I had to set it up so that I just had to type firefox within a console. So I created a symlink in my 'bin' folder with all my other custom perl scripts and other command line programs/scripts:

I also had to setup my fluxbox keybinding like so:

I originally was using "iceweasel" which is the Debian fork of Firefox, you can read why Debian had to fork Firefox on WikiPedia

I do notice a difference, pages load pretty fast and the FasterFox Plugin helps. However they packaged an extension called "AdBlocks" which I've never used and I don't really like. But for now I have just removed it.

Swiftweasel 2.0.0.4.1 (Default branch) - Swiftweasel is an optimized build of the Mozilla
Firefox Web browser for Linux. It offers builds
for both AMD and Intel processors. Swiftweasel is
100% compatible with all Firefox themes, plugins,
and extensions.
License: Mozilla Public License (MPL)
Changes:
The update notifications feature that made its
first appearance in 2.0.0.5pre is installed. When
a new version is available, you will be notified
so you can get it. Further font rendering
improvements were done. Automatic detection of
plugins is done in common directories in the file
system. A few more build tweaks were made. The
"Release Notes" option in the Help section brings
up the release notes.
[FreshMeat]