very good summary of the different types of schizophrenia: paranoid, catatonic, disorganized, and residual.

Obviously, this page is not designed for you to diagnose yourself, but it can definitely help you decide whether or not it's time to get medical attention. It can also help explain the reasons of a formal diagnosis.

This article introduces the dry DSM-IV criteria in a very readable manner -- terminology is tagged so you can click on it and read a bit more on what the word means.