My fisheye Lomo is great, but I haven't found a processing lab near my hotel. I got to thinking about ways to convert my Canon ixus 980 since I don't really use it -- it takes such boring shots out of the box... So I added a fisheye lens.
1. Obtain one of these
I got mine from an old guy in Bo Ai Lu, Taipei, for 700 TWD (a big Mac combo is about 100). He only had one, otherwise I would have bought a spare... as you'll see there's a strong possibility I'll need it! It's intended for video cameras, so it's about the right size for a P&S digicam.
2. Get some rubber bands
3. Stretch them out and pull them into the filter ring, which slides down leaving a gap
4. Turn the camera on and wait for the lens to extend
5. Pull the rubber bands over the camera, and start shooting!
6. Optionally, hold onto the lens so it doesn't fall off...