Because anyone can and will put anything up on the Web, it is vitally important to evaluate websites you'll use in your annotated bibliography or in any other academic assignment
Some things to look for include:
The Archer Library has a general guide on evaluating resources of all sorts here
The University of California at Berkeley Library have more criteria to evaluate resources here
Doing a Google or other search engine search gives tons of results, of varying quality
Try, instead, a Web directory that reviews the Web resources it gathers, such as ipl2: Information you can trust. They only include good resources in their directories
In the Web directory, you can either search by broad subject as given, or do a more precise search in the search box
Infomine: an American directory of reviewed Web resources for university students
Note: some of the websites Infomine includes are not free -- there will be a $ by a fee-based site