Rasheed Wallace is the best free agent big man out there. There is no close second. He can probably get more than the MLE if he wants it, but not if he wants another ring.
Who knows? Probably Sheed himself doesn't know yet where he'd like to play. Tell Garnett and Pierce to put their recruiting hats on.
I bet James Posey is avalable. In fact, I bet you could get him for Scalabrine and Tony Allen (both expiring).