A good free tool that checks over 140 social network and blogging sites to see if a user account is taken:
http://namechk.com/

Use: Enter some SEO friendly keywords and see where you can get account names using these keywords.

Refer to your Twitter Google Bomb report. While the report focuses on Twitter, the principles will work with just about all the social/blogging sites:
http://www.dombom.com/cgi-bin/dcforum/dcboard.cgi?az=show_thread&om=316&forum=DCForumID42