Cornell University Law School has posted an "annotated Constitution" with an extremely useful page dedicated to the First Amendment. It traces the First Amendment's legal evolution and provides concise summaries of the critical court cases.
The First Amendment Center maintains an educational website with extensive information and resources pertaining to the speech clauses of the First Amendment. Several freedom of speech issues are summarized, such as student rights and the First Amendment application to the arts. There are also lesson plans and links to relevant congressional reports and summaries of pending cases.
The American Civil Liberties Union tracks current First Amendment issues and cases on this site.