Most free agents that signed this off-season will be eligible to be traded March 1st, but there are exceptions like the restricted free agents from last season, and those who had offer sheets matched.
Another exception from Marc Stein's mouth:
PPS -- The contact extensions signed by Denver's Arron Afflalo and Detroit's Rodney Stuckey happened too late for either to be trade eligible this season, since March 19 (four days after the trade deadline) is when the restrictions on their respective contracts are lifted.
PPPS -- There are two more players who signed as free agents in January who don't become trade eligible until shortly after March 1: Dallas' Yi Jianlian (March 6) and Golden State's Nate Robinson (March 4). Players who sign after Jan. 16, such as the Clippers' Kenyon Martin, cannot be traded this season.
So no moving Stuckey even if we wanted to until this summer... bummer, was hoping to get some interest in him, but he's probably not moveable at this point.
And a side note of course, all Charlie Villanueva deals are welcome in this thread, but I reserve the right to call anyone who proposes one an idiot.