How to remove your Google Apps account
This depends on your situation, read & click further on the removal link.
Direct removal link: https://www.google.com/support/a/bin/answer.py?answer=1257646
Helpful Trick: Removing online data
Publicly visible text/images often aren’t properly removed even when you succeed in removing an account. Try editing or removing them manually before removing the account itself. If you’re unsure what happens to your tracks: this can be found mostly in the Terms of Service/Privacy Policy; otherwise you can always contact Google Apps and ask personally. By the way, removal requests don’t necessarily mean your data will actually be removed (e.g. due to legal obligations).
Helpful Trick: Remove third-party logins
If you signed up for Google Apps using a third-party login such as Facebook or Twitter, you probably want to revoke all access from Google Apps. Click here to find out how.