Tom Ziller has a list of the top 50 free agents available. You'll find a few Celtics on there.
Paul Pierce at #9 (early termination option)
Paul Pierce, a free agent? That's a new one. But given a few factors, The Truth could very well find himself on the market. It's his call -- he's under contract for $21.5 million in 2010-11, a massive sum he'd never grab on the open market at age 32. But Pierce is aging, and with the 2011 CBA looming this could be one last big contract opportunity. If Pierce opts out and wins a four-year contract for $12 million or so annually, he could very well come out ahead of taking $21 million and hoping for a deal under rougher circumstances, one year removed. Think Baron Davis in 2008. I would expect Boston would look to re-up Pierce if he does take the plunge.
Ray Allen at #14
Allen is certainly wrapping up his career, now in his mid-30s. The abandonment of his shooting stroke as 2009-10 moves along renders as both shocking and disheartening, given that's really all Allen had left in the first place. Perspective is in order, of course -- Ray hasn't been up to his lofty standard of offensive efficiency, but he's still better than a big portion of two-guards earning major minutes. While Ray can't (and surely doesn't) reasonably expect to top $10 million a season on the market, he can be a big boon for a good team, and you could see the power franchises bid him up a bit. It's unclear whether Boston would be a party to that, given the team's attempts to pawn him off for a younger asset at the trade deadline, and given the speed at which the core is crumbling. Allen could be a great fit with LeBron, wherever he ends up (including Cleveland ... heck, especially Cleveland).
Nate Robinson at #26
KryptoNate found himself in Mike D'Antoni's doghouse early in the season before breaking out and eventually getting himself traded to Boston. So far, he's had only a minor impact, playing few minutes and scoring few points. Since scoring is just about all N8 the Gr8 does, that's a problem. No NBA team can get away with starting him because of his size and lack of passing acumen, but in the right system he can be a great bench scorer. The market largely ignored Robinson in 2009, but there should be enough money out there to get Robinson a decent multi-year deal.
This is also a good place to start looking at what options might be available to us with either the MLE or at the vet. minimum. The tradeoff is clear in those slots. Do you take a quality veteran on the downside of his career (Grant Hill?) or a young player that has struggled to establish himself in the league (Randy Foye?)? I guess it depends on how the playoffs go, but I'd lean towards taking some chances on younger players looking for a fresh start.