Brian writes in…
Recently, I wanted to network my media center in the living room of my apartment. I was not satisfied with running an ethernet cable down the hallway and putting holes in the wall was not an option. Thats when I thought of running the cable through the air duct, my 555 based light-seeking robot came to the rescue!
More: The Biggest Little Chip – An introduction to the versatile 555 timer.
Tons of 555 timer projects!