In our house we always keep a few handy for those times when a screw gets stripped or simply when the hole for the screw is too large. Just insert one or more flat toothpicks into the hole in question, and the screw can be used again. It bites into the soft wood of the toothpick and securely holds.
Toothpicks are also great little glue applicators when you need to do some precision gluing in small spaces.
Here's a video with some other interesting ideas.
And here's a fun trick you can try with toothpicks. Just for kicks.