UPDATE: there were some issues with the first set of bundles which have been fixed. I've updated the links below.
All of the Tor Browser Bundles have been updated with Firefox 3.6.16 and the alpha bundles for Mac OS X and Linux have also been updated to use Libevent 2, as well as a number of extension updates.
All of the Tor Browser Bundles have been updated with Firefox 3.6.15 and the alpha bundles for Mac OS X and Linux have also been updated with Tor 0.2.2.23-alpha.
Note to 64-bit Linux Tor Browser Bundle users: The previous bundles contained Tor 0.2.2.20-alpha.
The Tor Browser Bundles have all been updated with some important security fixes and it is advised that all users upgrade.
There are new browser bundles out with the updated Tor versions (0.2.2.19-alpha and 0.2.1.27) that work with the latest OpenSSL.
We have some more new Tor Browser Bundles out. This is an upgrade to Firefox 3.6.12 which fixes a critical bug and OS X users' Torbutton will now show up.
We have some new Tor Browser Bundles out. The main notable upgrades for these are Firefox 3.6.11 and Pidgin 2.7.4 in the Windows IM bundle.