You can't go wrong with Shimano cranksets. I'm not sure what your price range is, but the integrated crank/bb LX/XT work well and are reasonably priced. If those are too expensive, the Deore crankset is may be a good option. For a non-integrated crankset, you'll just have to make sure your existing bb is compatible with the crank (square tapper, octalink, etc.).
How to remove/replace various cranksets:
http://www.parktool.com/repair/byreg...mageField2.y=7