mind puzzle

Ok, so there are two rooms connected by a closed door. You are in the room that contains three light switches, all initially in the "off" position. In the other room, where you can't see them, are three light bulbs matched up to the three light switches somehow. How can you figure out which light switch corresponds to which light bulb if you can only walk through the door once? (In other words, you flip some switches, you walk through the door, and you can't flip the switches anymore once you've opened the door.)

heh

"I am not in love. I am in a pre-romantic holding pattern."

Heard on some tv program just now.