Alaska at Large - Don Young.  The racetracker wiki states that Young "may retire."  The man dubbed the Prince of Pork (with Alaska Senator Ted Stevens as the King) is no longer a Committee Chair and he's in his mid 70's.  Young got one of his tougher races ever from neophyte Diane Benson in 2006.  The old crew who have run the state for the past 20 years are suddenly fading.  Former Senator and then Governor Frank Murkowski was badly beaten in a primary for re-election (finishing third).  Stevens son has been indicted IIRC and he's been raided by the FBI.  The last of the trio, Young, has merely lost his power base (so far).  

OR-2  Greg Walden is rumored, according to the wiki, to have state-wide ambitions in Oregon.  He may retire from a reasonably safe Republican seat to begin running full time for Governor of oregon (election is in 2010).

CA-41  Jerry Lewis is "reported" to be retiring according to Bob Novak (6/2/07).  Lewis appears to be a central figure in a web of defense contracting scandals starting with Duke Cunningham and extending outwards to other California Republicans in the House.  At the least, he was asleep at the wheel.  It seems more likely that Lewis was a key player in a major series of scandals.  Under another administration, he'd probably have been indicted already.

CA-42  Gary Miller ran unopposed.  That was before he was publicly under investigation by the FBI.  Yet another cog in the California Republican scandals.

CA-46  It seems like Dana Rohrabacher has been around forever.  He, too, is rumored to be connected with scandal, in this case the Abramoff?ethics variety.

CA-52  Duncan Hunter is running for President and is already taking steps to boost his son's chances for his House seat.

MT at Large - Denny Rehberg is rumored as a possible Senate candidate,

WY-  Barbara Cubin may be the state's least popular politician.  If she is on the list of three names to fill the current Senate vacancy, look for Democratic Governor Dave Freudenthal to appoint her (as the weakest possible Republican).  Some newspapers have said she is likely to be on the list.

CO-4  Marilyn Musgrave -  Racetracker reports that Musgrave, who barely was re-elected, is being pushed by Colorado Republicans to step down and make the party's chances in this normally safe seat stronger.

CO-6  Tom Tancredo is running for President.  According to the wiki he is probably not running for re-election to the House.

NM-1  The US Attorney scandal is swirling around both Heather Wilson and US Senator Pete Domenici.  On one hand, Wilson is rumored to be a Senate candidate, on the other hand she faces a very tough race against a charismatic Albuquerque pol, in Martin Heinrich.  Yes, there is certainly a good chance that one way or another this seat will be vacant.

AZ-1  Rick Renzi is not only under investigation but the political death watch has begun.  Will he make it to the end of his term?

PA-16  Joe Pitts is reported by 2008racetracker.com to have nearly retired before 2006.  Only heavy staff pressure allegedly kept him running.  With a Democratic House, this would be a good time for Pitts to hang them up.

PA-5 John Peterson  "Maybe not (rumors)"  racetracker wiki

DE-  Mike Castle had a stroke in 2006.  If his health is bad, he will likely retire.  If Joe Biden makes it onto the Democratic ticket, Castle could run for the Senate.

MD-6  Roscoe Bartlett  "Unknown.  Will be 82."

OH-16  Ralph Regula "Probably not... 84 in 2008."

IL-14  Denny Hastert  The lines are forming on both sides of the aisle.  Wiki states "Unlikely."

IL-16  Out of no where, La Hood is suddenly a candidate to become President of Bradley University.  Will La Hood play all his home games in Peoria?(MyDD)

MI-10  Candace Miller "Could run for Senator"

WI-5  Jim Sensenbrenner "Probably he might retire"

IA-4  Tom Latham  MyDD lists as a possible Senate candidate.

IA-5 Steve King  "Unknown"

MO-9  Kenny Hulshof "Likely" candidate to head the University of Missouri.

VA-1  Jo Ann Davis "In question due to a recurrence of breat cancer."

VA-11  Tom David will probablu either retire OR run for John Warner's Senate seat.

NC-6  "Howard Coble ... will be 77"

SC-1  Henry Brown  "Unknown.  Brown will be 73 in 2008 and he never served in the minority party."

LA-1  Bobby Jindal.  Jindal is running for Governor in 2007.  If he wins, the seat becomes vacant.

FL-10  C. W. "Bill"  Young.  Young has already served in the House for over 30 years.  He will be 78 in 2008.

TX-3  Sam Johnson  "Probably not.  Johnson will be 78 in 2008 and has only served three years in the minority."

TX-6  Joe Barton  "Unlikely"

TX-14   Ron Paul  Paul is running for the Republican nomination for President.  The Dallas Morning News reports that he is likely to file for his House seat again.

That is all for now, folks.