Apple has released iPhone Update 2.2.1.
The update corrects image importing from Mail in an instance where images are not saved into the Saved Images folder, improves Safari stability, and fixes an issue where Apple Lossless tracks would skip during playback in certain instances.
To update go into iTunes and select iPhone > Check for Updates
Encyclopedia: Apple iPhone/Apple iPhone 3G
Can’t say I’ve seen anything of significance in terms of user-visible changes.
The update may have been held back on iPhone to prevent unlockers from having the latest code. If you want to unlock your iPhone, don’t install this update until unlock viability is assessed.
However, jailbreaks should still be possible, redsn0w on iPod touch 2G should work with iPhones, assuming Apple updated the bootloader code across the board.
P.S. The first-generation iPod touch has also been updated to 2.2.1.