eh.... aren't the last 2 choices the same thing?
An agnostic is someone who isn't sure about his or her beleifs in gods or a God. Someone who is debating with themselves, or is working on making a decision or is just plain old saying "I don't have the answers so I won't worry about it".
Someone who believes in God but isn't a member of any organized religion might have a very strong set of beliefs, they just don't matchup with any of the sects.
Edit: I never understood the notion of a PROUD athiest. Why would you be PROUD of NOT believing in something? Why take pride in going contrary to the beliefs of others? Because without religion, there is no athiesm. Athiesm is not a belief system in and of itself. It is the OPPOSITE position of someone who DOES believe in God.
Perhaps the correct thing to say is your are a PROUD Rationalist. Or a proud believer in science. Declaring yourself a PROUD athiest is just begging to start an argument. Be proud of the things you DO believe, not the things you DON'T believe.