That's what I was doing two weeks ago. I made a trivet and coasters set with the leftover sock yarn from my Dad's socks. I then felted (fulled is actually the proper term) them, and needle felted some designs onto them. I used the pattern I found here. The coaster pattern was on the same blog. I was disappointed that they didn't felt squarely the corners were really out of proportion and I had a hard time blocking it. Ironically, my gauge swatch for the socks turned out the best (I threw it in to see what would happen). I think the crazy corners were probably knitter error, but I'm not sure what the error is.
I also worked on my own version of this. I have no idea what to call it, but it is supposed to help stop a door from slamming shut when the windows are open or the air conditioning is on. This is my first try, and a failure - the door still slams. I took notes on what to do to improve it and will have another go at it sometime soon.