iPhone Firmware Version 2.2 was released this morning, and as usual it is recommended you do not apply it until the Dev Team gets Pwnage tool and Quickpwn updated. Some of the new features include are:
Street View For Google Maps
Ability To Turn Auto-Correct Off
Ability to download Podcasts over the air.
Updated Safari Menu Bar
Walking And Bus Directions in Maps.
No copy or paste OR MMS

More to come as we see them...
ALSO: iTunes 8.0.2 Is out as well (Thanks to nickh for sending that in)
Onslaught of Direct Links ahead!
1st Gen Touch:
Here
2nd Gen Touch:
Here
1st Gen iPhone:
Here
iPhone 3G:
Here
Edit Poseidon: For 1st generation users that just can't wait for the updated pwnage/quickpwn... you can use the UPDATE feature iTunes and retain the unlock (no baseband update) and activation. You WILL lose your 3rd party apps and jailbreak.
The jailbreak for 2.2 is on its way soon according to the dev team - they just have to test to make sure it works fine, but they're fairly sure the Pwnage method is unchanged in 2.2.
If you are using a proxySIM (YES SIM, Universal SIM, etc) for your 3G unlock then DO NOT upgrade. The baseband gets upgraded and you proxySIM will NO LONGER WORK!
If you accidentally upgrade your 3G iPhone to firmware 2.2 there is NO WAY to downgrade because of the baseband update. You're STUCK.
admin edit: Remember, if you're jailbroken, DO NOT UPDATE quite yet!
-pf