What's the difference between pantheism, pandeism, deism, and atheism? Do all of them come back to actually meaning the same thing? If they're all different, what's the difference? If not the same, what other types of things like these are there?

Start with a normal dictionary. They distinctly do not mean the same thing. Off the top of my head, atheism is the belief that there is no god, and deism is the belief in some sort of god (actual god unspecified). The others sound (to me) like they are names for the belief in multiple gods.

At least one other word to add to your list: agnostic.

You can add the word Gnostic to your list also.

A good reference is Wikpedia. Try that resource.

Here's a good site to look those up (they are all different): Beliefnet.com