Here's a quick idea that I ripped off (most of it anyway) from Simon Phillips.
1. Play paradiddles in 8th notes, starting with your right foot.
2. While this is going on, play paradiddles in quarter notes with your hands.
3. Next play paradiddles in triplets against the 8th notes in your feet.
3. Finally keep the feet the same and play paradiddles in 16ths with your hands.
It's a nice challenge and gets your brain working.
Okay, back soon (I hope!)