Whitesell will turn 28 in April, so he's still in his prime. The problem lies in is his versatility; he can only play 1st base and DH. And at 1st base, he is just average defensively. I'm thinking the Oakland A's could be a good fit. Jack Cust will likely sign with a new team. Whitesell's main competition would be Daric Barton and Jake Fox, both of whom are unproven players. And we all know that Billy Beane likes guys who can get on base. Whitesell is one of those guys.
Whitesell reminds me a little of Micah Franklin, a JML from the last decade who put up great numbers in the Minors and was only given a taste of MLB in 1997 with the Cardinals. Hopefully, Whitesell's fate will not be the same as Franklin's.
EDIT: Whitesell has signed a Minor League deal with the Washington Nationals, the team that drafted him in 2003 (then the Montreal Expos).
Staying in the NL hurts Whitesell's chances of getting significant playing time, as there is no DH. Still, he would be a defensive upgrade over Adam Dunn at 1st base. As I said before, Dunn is a liability wherever you put him.
If the Nationals moved him back to the outfield and used Whitesell at 1st base, defensively their corner outfielders would take a hit with Dunn and Josh Willingham while their corner infielders would improve with Ryan Zimmerman and Whitesell. And I still believe Whitesell can be a major contributor at the plate if given a fair shake.