Well. You can use your own DVD that has a calibration setup, such as Finding Nemo.
That being said, a calibration DVD isn't a terrible idea either. If you can find one at not too terrible a cost, I'd go for it. You invested a lot in your tv, why not make it the best picture possible.
THAT being said, the best picture possible would be by professional calibration. Which I think is going over the top a little too much unless you spent like ten grand on your tv.