From nookDevs

Before Market will successfully download applications, it appears to be necessary to login to YouTube with an account ending with @gmail.com. Repeat, you will still need an @gmail.com account to make this work. After following this process Gmail, Calendar, Talk, Market, etc. will use your Google Apps account.

This process is very similar to the normal process with a few small additions. It must be completed in this order after first rooting. It should be possible to make this work by editing accounts.db and accounts.xml, but no one has worked out a reliable way to do this yet.

1. • Unlock the NC.
   • At the Android Welcome Screen tap the robot.
   • Skip "Learn how to use your LogicPD Zoom2"
   • Skip "Set up your Google Account"
   • Select both boxes for "Use Google Location" and click Next (Send anonymous data to Google check box may be optional)
   • Tap the white Nav Arrow > settings > Wireless & verify that you are connected to WiFi
     • (The Nav arrow is the white up arrow in the middle of the notifications bar at the bottom of your screen.)
   • Tap the Nav Arrow > extras > Youtube & accept the ToS
   • Tap the menu (to the right of the Nav Arrow), if the button doesn't work reboot your Nook Color. (This is a known bug in 1.0.1) & select "My Channel", then Add account & add your Google Apps account.
     • It is normal for YouTube to display a number of errors at this point.
   • Tap the Nav Arrow & extras & launch Gmail
   • In Gmail, tap menu > accounts > chose your account (may be optional)
   • Then menu > Refresh. Wait for sync. It takes a minute. You should see your Inbox. (If it fails to sync that is fine.)
   • Launch google Talk and be sure it connects (this step may be optional).
   • Tap the Nav Arrow > extras > Youtube.
   • Tap the logout option in YouTube.
   • Tap the menu (to the right of the Nav Arrow) & select "My Channel", then Add account & add your Gmail account.
     • When you log in, put in your entire gmail address, it must be of the form . Nothing else works. We really mean this.
   • Open up Market and Accept Terms and Service. You should be able to see market apps & download & install directly from the Market.
   • The core Google applicatins should now work with your Google Apps account. Note that it is normal for calendar to take a while to do it's first sync.
2. If you want to enable non-market install of software by applications like slideme and Astro, until auto-nooter is updated, you can follow the instructions at Enable on device installers