The following site has a list of names, I don't know when the list was published:
http://www.sovereignty.net/center/socialists.htm
Congressional Members of the
Progressive Caucus
Rep Earl Hilliard (AL-07)
Rep Eni Faleomavaega (AS-AL)
Rep Ed Pastor (AZ-02)
Rep Lynn C Woolsey (CA-06)
Rep George Miller (CA-07)
Rep Nancy Pelosi (CA-08)
Rep Fortney "Pete" Stark (CA-13)
Rep Henry A. Waxman (CA-29)
Rep Xavier Becerra (CA-30)
Rep Julian C. Dixon (CA-32)
Rep Esteban Edward Torres (CA-34)
Rep Maxine Waters (CA-35)
Rep George E. Brown (CA-42)
Rep Bob Filner (CA-50)
Rep Diane DeGette (CO-01)
Rep Eleanor Holmes Norton (DC-AL)
Rep Corrine Brown (FL-03)
Rep Carrie P. Meek (FL-17)
Rep Alcee L. Hastings (FL-23)
Rep Cynthia A. McKinney (GA-04)
Rep John Lewis (GA-05)
Rep Neil Abercrombie (HI-01)
Rep Patsy Mink (HI-02)
Rep Jesse Jackson (IL-02)
Rep Luis Gutierrez (IL-04)
Rep Danny Davis (IL-07)
Rep Lane Evans (IL-17)
Rep Julia Carson (IN-10)
Rep John Olver (MA-01)
Rep Jim McGovern (MA-03)
Rep Barney Frank (MA-04)
Rep John Tierney (MA-06)
Rep David Bonior (MI-10)
Rep Lynn N. Rivers (MI-13)
Rep John Conyers (MI-14)
Rep Bennie G. Thompson (MS-02)
Rep Melvin L. Watt (NC-12)
Rep Donald Payne (NJ-10)
Rep Jerrold Nadler (NY-08)
Rep Major Owens (NY-11)
Rep Nydia M. Velazquez (NY-12)
Rep Charles Rangel (NY-15)
Rep Maurice Hinchey (NY-26)
Rep John LaFalce (NY-29)
Rep Marcy Kaptur (OH-09)
Rep Dennis Kucinich (OH-10)
Rep Louis Stokes (OH-11)
Rep Sherrod Brown (OH-13)
Rep Elizabeth Furse (OR-01)
Rep Peter A. DeFazio (OR-04)
Rep Chaka Fattah (PA-02)
Rep William Coyne (PA-14)
Rep Carlos A. Romero-Barcelo (PR-AL)
Rep Robert C. Scott (VA-03)
Rep Bernard Sanders (VT-AL)
Rep James A. McDermott (WA-07)