heres a great way to check and see if your battery is bad or worn out. get a DVOM or voltmeter. put the leads on your battery + and - terminals. Hop in and crank it up, if the voltage on your battery drops below 9v while cranking, its on it way out and you might as well go on and replace your battery.
on another note, anybody who does work on their car needs to get a DVOM and keep it in their car somewhere. This is a great example of why they are so handy to have. Its obvious the issue is either w/ your battery or Alt. but say your starter fuse blew or the ground to your starter soleniod mysteriously came loose. Instead of getting your car towed off you might be able to fix a small problem on your own and save yourself plenty of time and trouble by being able to check things out yourself
"chaosProtege--- if the starter is clicking, its not normally bad. bump start your car, if it starts the starter is good. check the wiring to the alternator, too"
If you hear the clicking that means the solenoid is good, not the starter, they're 2 different things;
Your car will roll start without a starter being bolted on, being able to roll start a car does not indicate whether or not your starter is good or not
Titanium- your very right about that one, it is horrible to remove a battery while the car is running. On a good bit of new cars the alternator is controlled by the PCM, well the pcm sees if the alternator is doing its job through the battery, if the battery isn't their the ECU freaks and tells the alt. to run at full capacity = trouble
I had a person who brought in a 01 galant that had removed the battery too see if his alt was good. his alternator was good, but his 1000$ ecu wasn't after that