Patrick O'Donnell, a blogger over at Ratio Juris, has posted this very useful Comparative Law Bibliography online. I've added a link on the sidebar. Other bibliographies on Ratio Juris include International Law and Human Rights. The Comparative Law Bibliography's headings are: (1) Comparative Law: Assumptions, Topics and Theories (2) Law in Africa (3) Chinese Law (4) Hindu Law (5) Islamic Law.
Tips on other comparative law bibliographies or research guides are very welcome.