In case you missed the Part I from yesterday (showing the ratings from '08 Presidential contenders), here's my reasoning for averaging the ADA & ACU, and for not including other ratings from organizations such as the National Journal:

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Why the ADA & ACU?  They have among the longest history of doing such vote ratings, the ADA having released ratings back to 1948, the ACU since 1971.  This allows for historical comparison with Representatives & Senators of the past 50 years using fairly similar criteria.  Plus, the groups aren't particularly focused on one issue or another.  Rather, one advocates liberal causes, the other, conservative causes.  By averaging the two, I think you reach something close to a good idea where a member of Congress stands.  And yes, I have pondered adding other ratings, such as the National Journal's and Congressional Quarterly's rankings.  I leave them out because (1) there's not as much history, (2) especially in the National Journal's case, I'm not hot on their methodology (evenly spacing out all members instead of showing exactly how liberal or conservative a member is) and (3) it takes long enough averaging the numbers of 535 Representatives & Senators from 2 organizations, much less adding a 3rd or 4th.

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Now, onto the Senate.  These are the ratings through the last session of the Senate, in 2006.  Therefore, I've included Senators who retired or were voted out of office.  Retired Senators are marked with a #, Senators who lost re-election marked with a ##.  

I've included Joe Lieberman as a Democrat since he still was one last year.  In future years, he'll be noted as an Independent, or whatever he decides to call himself.  

Speaking of party-switching, the ratings for the two Senators who have switched affiliations are for their time since the switch (Richard Shelby since he became a Republican, Jim Jeffords since he became an independent).  I consider it a more accurate reflection of where they're at now ideologically.  In parentheses after their rating, I've included their entire lifetime ratings going back to when they were a Democrat and Republican, respectively (you'll notice Shelby has a higher number when you include his days as a Democrat, and Jeffords has a lower number including his GOP years).

In case you didn't see it, here's Part I from yesterday:

Part I:  '08 Presidential Contenders

Here we go, the Senate:

Barbara Boxer  (D-CA)      96.5
Chuck Schumer  (D-NY)      95.1
Barack Obama (D-IL)        94.8
Frank Lautenberg  (D-NJ)      94.4
Edward Kennedy  (D-MA)      94.4
Barbara Mikulski  (D-MD)      94.1
Patty Murray  (D-WA)          94.1
Jack Reed  (D-RI)          94.0
#Paul Sarbanes  (D-MD)          93.8
Pat Leahy  (D-VT)          93.7
Hillary Rodham Clinton  (D-NY) 93.4
John Kerry  (D-MA)          93.4
Carl Levin  (D-MI)          92.8
Russ Feingold  (D-WI)         92.8
Daniel Akaka  (D-HI)          92.2
Tom Harkin  (D-IA)          92.2
Deborah Stabenow  (D-MI)      92.1
Dick Durbin  (D-IL)          92.0
Robert Menendez  (D-NJ)    91.2
#Mark Dayton  (D-MN)          90.9
Maria Cantwell  (D-WA)      90.7
Ron Wyden  (D-OR)          90.4

#Jim Jeffords  (I-VT)         89.6 (72.1)
Chris Dodd  (D-CT)          89.3
Dianne Feinstein  (D-CA)      88.8
Herb Kohl  (D-WI)          88.1
Jay Rockefeller  (D-WV)      87.7
Tom Carper  (D-DE)          85.2
Byron Dorgan  (D-ND)          85.2
Jeff Bingaman  (D-NM)      85.0
Ken Salazar (D-CO)        85
Daniel Inouye  (D-HI)          84.2
Tim Johnson  (D-SD)          83.2
Evan Bayh  (D-IN)          82.4
Blanche Lincoln  (D-AR)      82.2
Max Baucus  (D-MT)          81.5
Joe Lieberman  (D-CT)          81.2
Joe Biden  (D-DE)          81.0
Kent Conrad  (D-ND)          80.9
Harry Reid  (D-NV)          80.0

Mary Landrieu  (D-LA)      79.5
Bill Nelson  (D-FL)          79.2
Mark Pryor  (D-AR)          78.3

Robert Byrd  (D-WV)          67.6
##Lincoln Chafee  (R-RI)          64.9

Arlen Specter  (R-PA)          54.6

Ben Nelson  (D-NE)          49.2

Olympia Snowe  (R-ME)      46.3
Susan Collins  (R-ME)          42.9

Ted Stevens  (R-AK)          27.5
Norm Coleman  (R-MN)      24.9
Lisa Murkowski  (R-AK)      22.7
Gordon Smith  (R-OR)          23.3
George Voinovich  (R-OH)      20.8

##Mike DeWine  (R-OH)          19.9
Pete Domenici  (R-NM)          19.1
John Warner  (R-VA)          15.9
John McCain  (R-AZ)          15.9
Richard Lugar  (R-IN)          15.5
Thad Cochran  (R-MS)          15.4
Charles Grassley  (R-IA)      14.3
Kit Bond  (R-MO)          14.2
Judd Gregg  (R-NH)          14.2
Chuck Hagel  (R-NE)          12.2
Lamar Alexander  (R-TN)      12.2
##Rick Santorum  (R-PA)          11.2
Robert Bennett  (R-UT)      10.8
Elizabeth Dole  (R-NC)          10.8
Lindsey Graham  (R-SC)      10.5

Richard Shelby  (R-AL)         9.5 (22.6)
Pat Roberts  (R-KS)          9.4
John Thune (R-SD)        9.4
#Bill Frist  (R-TN)          9.3
##George Allen  (R-VA)          8.3
##James Talent  (R-MO)         8.3
Orrin Hatch  (R-UT)          8.5
Kay Bailey Hutchison  (R-TX)      8.4
Mitch McConnell  (R-KY)      8.2
John Ensign  (R-NV)          8.1
##Conrad Burns  (R-MT)          8.1
Craig Thomas  (R-WY)      8.0
Johnny Isakson (R-GA)        8.0
Richard Burr (R-NC)        7.7
Michael Enzi  (R-WY)          7.1
John Sununu  (R-NH)          7.0
Mel Martinez (R-FL)        6.3
Trent Lott  (R-MS)          6.2
Michael Crapo  (R-ID)          6.0
John Cornyn  (R-TX)          6.0
David Vitter (R-LA)        5.2
Sam Brownback  (R-KS)      5.0
James Bunning  (R-KY)      4.9
Larry Craig  (R-ID)          4.9
Tom Coburn (R-OK)        4.5
Saxby Chambliss  (R-GA)      4.0
Wayne Allard  (R-CO)          3.9
James Inhofe  (R-OK)          3.7
Jeff Sessions  (R-AL)          3.2
Jon Kyl  (R-AZ)          2.8
Jim DeMint (R-SC)        2.6

By the way, in case you're curious, some of our new Senators from the 2006 elections, those who came from the House, have the following ratings:

Bernie Sanders (I-VT) 95.7
Sherrod Brown (D-OH) 91.8
Ben Cardin (D-MD) 91.4

As always, merely one more way to look at the ideological make-up of Congress.  Any questions, I'll try to answer them.