Bottle of Simple Green, some shop towels and some engine de-greaser for the tough spots.
I use 80psi air to blow all the crap out of the engine bay, then attack it with de-greaser (doenst work though so i dont even know why i do this, NYC street grime is teh secret ingredient in truck bed liner) then water. Honestly though, the only time i wash my bike is after a rainy ride. other wise its usually 3 mins of a garden hose trying to get all the sand and pollon of it.
You should see someguys bike. that thing was never washed.