Try some simple tapping riffs like this... They'll force you to go a lot faster than picking and you'll get more exercise in the pinky and third finger cause you have to hammer each note.

|---p5--h8--t12---p5--h7--t12--|

There's a bunch more here:

http://www.guitartricks.com/2000/trick.php?trick_id=1873&s_id=13