I've recently been discovering the fun of bouncing an on-camera hot-shoe flash with the AF-540 attached to the K20D.
You can easily get some keen results like this... 0.8 sec, F/5, iso 400
With a steady-hand you can drag the shutter and use a slow shutter speed. This helps to balance the flash with the ambient light. The flash will help freeze motion.
For a clue on how I did it, here's a 100% crop...
I angled the flash backward, over my head and at an angle.
Here are a few more examples of bounce flash.... all of these were taken in my fairly dimly lit living room at night.. just enough light to lock focus on dark colored doggies.
Now then, grab your camera and try it!