For the 555 contest, I have made a pinball machine. Sadly I ran out of time before I could get everything in and working. I do have the SiniScore 555 and several elements on the playfield work. Previous blog entries detail the build. Here is a picture of the playfield as it is right now:
Also, here are the latest schematic images:
Here's a picture of the breadboards with the above circuits:
It uses 13 555s in that configuration. The final version if I had gotten everything in and working would have used about 25 of them for the main functionality, and a dozen or so more for the LED lighting (flashers and such) and sound effects.
Here is a short video showing what I have working: