Look in the yellow pages for Fix-a-Dent or Painless dent repair. I have seen them take out hail damge dents and you would never know it was ever dented. Make sure you check the local reputation as this kind of work involves skill.
If the paint ain't cracked or anything like that, you might be able to get away with something as simple as a plunger. I did it on my uncle's truck a few times and it worked great. works best if it's a smooth dent and the paint isn't cracked.