An annotated biibliography is a list of citations to articles, books or other documents. Each citation is followed by a brief (about 200 words) descriptive and evaluative paragraph, the annotation (summary of the source indicating why it is relevant to your research). The purpose of the annotation is to inform the reader of the relevance, accuracy, and quality of the source cited.* Try these sites for help with annotated bibliographies.
*C. Marin, course syllabus
Ithaca College has a couple of great resources on Annotated Bibliographies:
Their guide to Annotated Bibliobraphies
Their interactive tutorial
The Olin and Uris Libraries at Cornell University have created an excellent guide to how to prepare an Annotated Bibliography.
The "Owl" writing lab at Purdue University also has information on creating an Annotated Bibliography