New! Google help register one domain for $10 when you sign up google Apps (Free)

Google Apps for Your Domain lets you offer private-labeled email, instant messaging and calendar accounts to all of your users.

It’s all free* and everything is hosted by Google. No hardware or software required.
New! If you don’t have an internet domain yet, google can help you register one for $10 when you sign up for Google Apps for Your Domain.

more info

http://www.google.com/support/a/bin/answer.py?answer=53929&topic=10407