It looks like the D’s are going to fall just short of that mythical 60 votes in the Senate. At this point, 58 seems likely, 59 a possibility given how close MN is. Subtract one for Lieberman. However, the Senate is a coalition-building body, and Reid and the Obama Administration will probably want to / need to bring a few Republicans along on major Legislation.
Likely targets? Senators up for reelection in 2010 in states that Obama won:
Mel Martinez of FL
Charles Grassley of IA
Judd Gregg of NH
Richard Burr of NC
George Voinovich OH
Arlen Specter of PA
McCain is also up for reelection in 2010 as well.
You could see several of these guys feeling vulnerable and maybe signing onto certain Obama agenda items to pass bills through the Senate.