Project Muse
This is an index of full-text journals on wide range of subjects in the liberal arts. The cite includes excellent essays on almost everything concerning Shakespeare and his plays. Just login with your X500 and search.
Criticism of Individual Plays
This is a link from "Mr. William Shakespeare and the Internet." The cite provides popular criticisms on nearly every play. If you're interested, _The Merchant of Venice_ link has a few criticisms on Shakespeare and anti-semitism.