I started the car, but now I can't turn the key back and shut off the engine. The engine is still running. Is there anything i can do?

It's a 92 Saturn SL1 automatic

 

You might try LIGHTLY tapping on it with a hammer. IF that doesn't work, just disconnect your battery ground cable. If that does work, try putting some graphite in the ignition cylinder and rotating the key back and forth a few times. This will lubricate the tumblers in it.

 

Per Rube,

Powdered graphite in small tubes are available at Lowe's and Home Depot.
Ask someone from the lock/key dept.

 

Thanks for the help. Disconnecting the battery stopped it. I couldn't get the cylinder to move like it should so it looks like it'll be a replace job.

 

See if you can find a kit with the removable tabs for your original switch. You simply disassemble the old one, one tab at a time, clean off the old one and check the # or letter on it and put in a new one with the same # or letter. After you get them all in, your old key should still work in the switch. If you can't find a kit like that, then you'll just have two keys on your key chain, instead of one.