http://sites.google.com/support/bin/answer.py?hl=en&answer=99448

Log in to the site
Under "More Actions..." choose "Manage Site"
Choose the "Web Address" Option on the left nav sidebar
Add the new web address (must have a subdomain like www.)

Make the CNAME change at your registrar

http://www.google.com/search?client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&channel=s&hl=en&source=hp&q=forward+domain+to+blogger&btnG=Google+Search
forward domain to blogger - Google Search
http://www.consumingexperience.com/2008/02/blogger-how-to-use-www-custom-domain.html
Blogger: how to use a www custom domain for your blog - A Consuming Experience
http://www.google.com/search?q=forward+domain+name+to+google+sites&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a
forward domain name to google sites - Google Search
http://www.google.com/support/a/bin/answer.py?hl=en&answer=61057
URL forwarding - Google Apps Help
http://sites.google.com/support/bin/answer.py?answer=99447
How can I change my site URL to www.mydomain.com? - Google Sites Help
http://knol.google.com/k/larry-h/google-apps-discussion-group/2ywrfjibsoohc/1#view
Google Apps Discussion Group - a knol by Larry H
http://sites.google.com/support/bin/answer.py?answer=99450
Changing the site URL for sites created under sites.google.com/site - Google Sites Help