According to cqpolitics:
Democrats have 186 safe seats.
Republicans 150 safe seats.
The way things stand now, Democrats need to win those safe seats plus 32 out the 60 seats that either Democrats are favored (37) or leans towards them (23).
This doesn't include the 13 toss-up races. Though these generally break one way or the other.
current situation: 257 178
CQ's current projection: 246 176 toss ups 13
Newliberal prediction 249 186
Democrats will win in 2010! republicans will gain only 8 seats.