How to Prepare an Annotated Bibliography - Cornell University Library
A clear, concise introduction to preparing an annotated bibliography. An excellent place to start.
Writing Annotated Bibliographies - U. Wisconsin-Madison Writing Center
A very detailed and extensive site, covering all sorts of aspects of writing an annotated bibliography. A wide range of options, approaches and possibilities. Complete with examples.
Annotated Bibliography - LEO, St. Cloud State University
Useful general basic guidelines. Not as extensive as the Wisconsin-Madison site, but more manageable in size. Also a little more prescriptive, which can be good if you are confused or annoying if you are more confident.