Further, possible-to-likely Senate candidates are emerging in traditionally red states:

Indeed, September could prove a very decisive month in terms of shaping the 2008 Senate races.  This week also saw a plethora of interesting news around the country:

South Dakota: Senator Tim Johnson returned to the Senate floor and made his first roll call vote in almost nine months.  Badlands Blue has the video of his return, including a nearly-minute-long standing ovation before Johnson spoke and another minute of standing ovation after Senator Johnson's comments.  Truly uplifting.
Delaware: Senator Joe Biden is definitely moving forward with Senate re-election plans amid his Presidential campaign.
Texas: Though a majority of Democratic primary voters are still undecided, State Representative and Lieutenant Colonel Rick Noriega currently has about double the support of attorney Mikal Watts, 27-14.  Attorney Emil Reichstadt, who may soon exit the race, clocks in at 6%.  Noriega also recently scored the support of Texas' firefighters.
New Hampshire and Minnesota: In case anyone thought otherwise, both Sprintin' John Sununu and Smilin' Norm Coleman are still George W. Bush's lapdogs on Iraq.
Alaska: Ted Stevens appears to be both a climatologist and a sociopath.  All of that insane behavior may just be to deflect attention from his latest earmark scandal.
Colorado: Backwards Bob Schaffer's own poll numbers see him losing to Democratic Congressman Mark Udall by more than the margin of error.  Schaffer's camp is trying to spin this as a good thing!  I can't wait for the non-partisan numbers to come out.
Louisiana: The candidate filing period for 2007 passed this week in Louisiana, and Republican state Treasurer John N. Kennedy is running unopposed for re-election while looking ahead to a possible 2008 Senate challenge to Senator Mary Landrieu.  Given Treasurer Kennedy's chronically mercurial career goals, hopefully someone in the Louisiana media can get him to answer questions like "If re-elected to the Treasurer's office, do you pledge to serve out your full term?" and "Why should the voters of Louisiana re-elect you if you're just going to run for another office in a few months?"  So far, all that has gone on the record is:

Kennedy declined to speculate on his political future, and would not commit to serving out his entire four-year term.

"I've never made promises about things in the future that I can't control," Kennedy said, adding that he wanted to savor re-election before looking ahead.

Hey, John, running for Senate isn't an involuntary action like sneezing or yawning - you do actually have control over whether or not you run for Senate. Totally disingenuous.
Virginia: A VA-GOP Senate primary between Tom Davis and Jim Gilmore could get very ugly.  The Club for Growth is already attacking Tom Davis' economic record.  Meanwhile, Davis' campaign has apparently hired adviser Chris LaCivita, whose claims to fame include advising and producing commercials for the notorious Swift Boat Veterans and serving as direct supervisor to the man responsible for the infamous New Hampshire phone jamming scandal.  This could be a historically ugly primary.
Kentucky: The Public Campaign Action Fund released an ad highlighting Mitch McConnell's record supporting the use of taxpayer dollars to fund iPod-like music players for Afghani tribesman but opposing body armor for our troops.  (Yes, you read that right; Ditch Mitch KY explains.  It of course involves a former McConnell staffer becoming a lobbyist, and McConnell securing an earmark for the clients of his former staffer while the lobbyist/former staffer raises thousands of dollars for McConnell.)  So what does McConnell do?  He uses his contacts and clout to get the ad pulled from cable stations!  In a completely unrelated note, Dictionary.com defines "fascism" as "forcibly suppressing opposition and criticism."
Arizona: Looking ahead to 2010, popular-but-term-limited Governor Janet Napolitano has established a federal political action committee, seen as an early step toward a 2010 Senate bid.  Meanwhile, early polling sees Governor Napolitano handily defeating John McCain by double digits in a hypothetical 2010 Senate match-up, 47-36.

Some parting notes:

For daily news and updates on the U.S. Senate races around the country in 2008, check out Senate 2008 Guru: Following the Races.