The National Journal has assigned liberal/conservative rankings to members of the House and Senate which were reported in the Denver Post, based on votes on several dozen key votes. The rankings (100 is the theoretical maximum conservative position, 1 is the most liberal theoretically possible liberal position).
Wayne Allard (R-CO) 90.8 (tied with Tom Coburn (R-OK) & Jeff Sessions (R-AL) for most conservative).
Ken Salazar (D-CO) 39.8 (centrist leaning liberal)
The full Senate rankings are here. The only Senate Democrats more conservative than Salazar are Mary Landrieu (LA), Kent Conrad (ND) and Mark Pryor (AR). Lincoln Caffee, the most liberal of the Republicans in the Senate rates 40.8. Joe Lieberman rates 34.3 (Lieberman is the most conservative Democrat on foreign policy, moreso than two Republicans, but is relativel liberal on social and economic issues). Former Republican Jim Jeffords rates a 22.2.
Marilyn Musgrave (R-4th CD) 90.8 (22 representatives are more conservative)
Joel Hefley (R-5th CD) 82.0
Bob Beauprez (R-7th CD) 73.3
Tom Tancredo (R-6th CD) 63.7 (55 Republicans are more liberal)
John Salazar (D-3rd CD) 40.5 (26 Democratic representatives are more conservative)
Mark Udall (D-2nd CD) 31.3
Diana DeGette (D-1st CD) 11.8 (46 representatives are more liberal)
Tancredo is a reliable social conservative, but leans liberal compared to his colleagues (according to the National Journal) on economic and foreign policy issues. Beauprez is listed as more liberal on foreign policy than on economic and social issues. Diana DeGette is particularly liberal on social issues compared to the economy and foreign policy. Salazar is relatively even across the board, as are Udall, Hefley and Musgrave.
Full results from the House here.