A couple of things I've been playing with, trying to learn to write music:
1) Just doing a melody, single notes, right hand. Nothing too complicated, (and certainly nothing to write home about yet), but it lets me think more about rhythm and timing and such.
2) Putting some chord in the left hand, and keeping the melody going, single notes, with the right. This gets me thinking about chord progressions, which many melodies certainly seem to imply as they go along.
Something occurred to me on the drive to work today, namely that learning to play somebody else's music will help you get the ideas into your head, and be able to create your own, but learning to play the music that you create (as you create it, even) is several times more efficient (at my stage) at developing creative muscle.
And as I've said before, the more I have my hands on the keyboard, the better I'll be at playing, even if I'm not thinking about "performance" proper.