For a comprehensive review and index of items involved with searching for alternatives, visit the University of California - Davis Center for Animal Alternatives.
ALTWEB is a great site for news, information, discussion, and resources from the field of alternatives to animal testing. A joint effort of Johns Hopkins CAAT and a number of other public and private organizations, it is intended to foster the development of scientifically acceptable in vitro and other alternatives to animal testing.
The NORINA database provides audiovisual alternatives to the use of laboratory animals in teaching, including books, audiotapes, videotapes, CD ROMs, films, computer programs etc. It has an efficient search engine and provides extensive information on resources, including a detailed description of the contents, source, price, audience suitability, etc.
The Interagency Coordinating Committee on the Validation of Animal Models ( ICCVAM ) site provides information on models that have been validated, those under development, and how the process works.