I went out this morning to start it for work and *click* is all I got. Light and everything came on, and when I hooked a charger up to the battery it read 100%. What could be the problem, I mean, it started and ran fine the day before. I heard something about the starter freezing up, so maybe that's possible. It's been 0-20 degrees the past week or so here in OK.

 

There is a number of places to start on this based on the discription, but the first place I would start is to remove the battery cables, clean the terminals of corrosion and then re-assemble everything.
It would help to know if you are able to do any troubleshooting using a volt meter or something like what happend to the head lights if you turned them on and then tried to start the car while watching the head lights to see if they stayed on or went out. And then came back on when you released the key from start.

 

The possibility of a bad main battery cable cannot be overlooked. The side post batteries on Saturns will (over time) leak enough to cause the interior of the battery cable to rot out (kinda like termites). Simply put, may need to replace the cables ....