There's nothing that halts progress on a DIY project like a stripped screw. It's incredibly frustrating to get out, and that's just the beginning of your problems. Once it's out, you might also have to fix the hole if you want to use it for anything else.
There are tons of ways to do this, but if you're looking for something quick and simple, Chris over on Man Made DIY has you covered.
All you have to do is cut a piece from a wooden dowel that's the same size as the hole, then use wood glue to attach it. Once it dries, just sand it down or cut off the excess so that it's flush.
That's it! Now you should be able to drill a small hole and replace the screw with no problems. Check out Chris's article for more details.