Since this thread has already been brought back from the dead, I figured, why not do it again?
I had something similar happen last night, but the cause wasn't the battery. I drove home from work, 20 minutes later I go out and turn the key...nothing. When I pull the key out the gauges start going crazy like mentioned above. I checked my battery voltage, it was a little low but far from dead (it's a 5 year old battery). I cleaned up the terminals and connections like JDsDream said, and boom, it fired right up! Sweet, right? Not quite.
I started driving around to make sure everything was good, turned on the radio, then flicked on my headlights and my radio turned off and back on again. I could do this repeatedly while driving down the road. When I got back home, with the engine still running, the voltage on my battery was the same as if my engine was shut off. I figured my alternator had crapped the bed. I went to the local auto store, they checked the battery and alternator and confirmed this. Battery was still fine, but the alternator was toast.
I just followed this thread to replace the alternator and belt:
About an hour later, she fired right up, and no more issues with using the radio and headlights, and voltages look good, both on and off. Thanks everyone for helping me troubleshoot!