The Mozilla Project has released Firefox 1.5.0.8, Thunderbird 1.5.0.8, and SeaMonkey 1.0.6. These releases fix security flaws, and all users should upgrade. You should be able to upgrade just by going to Help/Check for Updates..., though when I tried that in Thunderbird it failed:
For Firefox users, I recommend jumping straight to 2.0. It's a much nicer browser that doesn't have the flaws in the first place.
The Mozilla Project has also posted the first beta of SeaMonkey 1.1. SeaMonkey is the continuation of the integrated Mozilla suite, and has XML support roughly equivalent to Firefox 1.5 (e.g. XML, XSLT, CSS, XHTML, etc.) It also bundles an e-mail client, web editor, browser, and more into one application. Particularly notable in this release is that "Message labelling has been superceded by tagging, which provides much more than the original 5 labels and comes with new preferences." That's almost enough to make me switch, but I suspect I'll hang on with Thunderbird until version 2.0 or Eudora 7 comes out. The current Thunderbird is crash prone, feature-poor, has horrible user interaction, and is ridiculously slow for no good reason but at least it doesn't seem to lose my e-mail.
