Just a quickie since I get this question a lot. My standard answer is: whatever the heck you want. People wore anything and everything last year.
Don't believe me? Check out the 2009 album.
Some of my favorites from that slideshow (click to enlarge):
Attack of the couch cushions
Jordan blending in with half the men on the ship
Yes, you can wear your bikini for the photo op. Why not?
Everyone wants a lap
I don't even know what's happening here
Anyway . . . what are you planning to wear?