Pallet wood is great to use for projects. They are free or close to it all the time. Just make sure there isn't any oil or chemical stains on them...it happens far to often. You just don't know what the chemical was so might be something you don't want in your house.
If you find a local source who only imports items and then needs to get rid of the pallets many times they may be a single use item even which means it's basically new wood for you to use.