Instead of taking your car to the mechanic, save yourself some money by going MacGyver and creating your own suction-style car dent puller from objects you've got laying around at home. All you need is a pot (or bucket), a vacuum cleaner, and some tape and you're pretty much set.
Following lr10cent's guide on Instructables, start by going underneath the pot (or bucket) and creating a small hole. Just make sure the hole is small enough that the mouth of the vacuum cleaner will completely enclose it.
Proceed by taping the the top edge of the pot around the dent, until it's as airtight as can be. Place the vacuum cleaner hose over the hole underneath the pot, turn your vacuum on, and wait until the the suction gets the dent out.
If nothing happens, you can try shifting the vacuum hose around a bit in order to let some air in. This can help improve the vacuum cleaner suction.