420 Clock

Update (12/21/2010) - You can install Gingerbread as per the instructions in this video. The only thing you won't have to do is flash a radio (Gingerbread uses the 2.2 radio).

Video volume is set at 20%. So if you turn it up, don't forget that you did, or else your ears will cry later :p
This also works if it's your first time flashing any version after 6.0. (6.1, 7.0, etc.)

Timeline to find the parts you need:

0:10-0:35 - Files to SD
0:36-2:16 - Nandroid Backup
2:17-2:38 - Optional App Backup
2:39-3:40 - Update Radio
3:40-4:20 - Data Wipe
4:20-5:45 - Flashing CM6 with Clockwork Recovery (Pick this or Amon_RA)
6:20-7:35 - Flashing CM6 with Amon_RA (Pick this of Clockwork Recovery)
7:35-8:05 - Flashing Gapps with Amon_RA (Pick this or Clockwork depending on which you picked for the ROM)
8:05-8:39 - Flashing Gapps with Clockwork Recovery (Pick this or Amon_RA depending on which you picked for the ROM)

COMPLETE! :D