Here's a simple coffee table I made out of an old, ratty stop sign and some birch plywood.
I was given a pile of old road signs a few years ago, which I have really enjoyed using for projects such as this one.
If you're interested in getting some old, used road signs (ahem, legally) for a project like this, I recommend asking small-town street departments. My experience has been that bigger cities actually take the time to haul them off to recycle, while smaller towns just throw their damaged and replaced signs in a pile somewhere. If you ask the right people, they'll generally be happy to let you haul off their trash. That's how I got mine!
The surface of this particular sign was relatively clean and flat, but had a lot of scrapes and stains from whatever it went through in its life. I thought the contrasting character between the abused old sign and the nice clean wood would be interesting.
It's a fairly simple design that should be easy to duplicate with some basic tools. If you make something similar, be sure to let me know in the comments. Thanks for taking a look!