Please note, VRDs are themselves websites and as such vary in terms of content and arrangement. Accurate Eye's Fact Finder Argus Clearinghouse One of the most selective. Guides done by subject librarians. Can be browsed or searched. Brief descriptions of the sites reviewed.
References range from the comprehensive to the specific.
A good starting place. Scholarly Internet Resource Collections Produced by the University of California at Irvine. Covers nearly 10,000 scholarly Internet resources. Organized into ten broad categories and subdivided below that. Can be browsed or searched by subject, keyword, or title.