Well, you could start with this group:
http://bsimmons.wordpress.com/2006/10/21/the-progressive-caucus-is-an-organization-of-members-of-congress-founded-in-1991-by-newly-elected-representative-bernie-sanders-independent-vermont-the-former-socialist-mayor-of-burlington-and-a-membe/
Oh great...one of those is in my state...McDermott. I knew he was bad news...this is just shows his hole is deeper than I thought.