Agreed. If the key won't turn, it's likely that the steering wheel is locked. Simply turn the wheel slightly/jiggle it while attempting to turn the key.

Also, if it is an auto, be sure that it is in park.

By the way - since you can't turn the key at all, does the car still make a beeping noise when you insert the key into the ignition, but leave the door open?

I would highly suggest double-checking the fuses, especially the fusible link (if it's got one, which I'm sure it does). Be sure to check the fuses both in the car and in the engine bay. New subies still have them in both places, right?

If all else fails, I would agree with previous posts on disconnecting the battery for about 24 hours to reset all computer control modules. In the mean time, get yourself a cheap multimeter or 12v battery checker-thingy.