Jeff Euston of Cot's Baseball Contracts recently posted an unofficial list of players who will become free agents after the 2011 season. That free agent class will be highlighted by a trio of first basemen: Prince Fielder, Adrian Gonzalez, and Ryan Howard, though there's a chance Albert Pujols will join them if he and the Cardinals can't work out an extension.
Some other notable players scheduled to become free agents after 2011 include Jason Bartlett, Carlos Beltran, Mark Buehrle, Edwin Jackson, Heath Bell, and Jonathan Papelbon. Robinson Cano, Yadier Molina, Grady Sizemore, and Matt Cain may also become free agents if their club options for 2012 are declined.
Obviously a lot will change between now and then, but it's never too early to look ahead!