- Librarian's Index to the Internet
- A searchable, annotated, subject directory of useful and reliable reference sites. Over 3600 Internet resources evaluated by librarians for the Berkeley Digital Library Project.
- Internet Public Library Reference Collection
- An annotated collection chosen to help answer specific questions quickly and efficiently. Sources are selected according to ease of use, quality and quantity of information, frequency of updating, and authoritativeness. Browse by subject, by title or search by keywords.You can also ask questions and receive answers by email.
- Refdesk.com
- You can read the review of this site from College & Research Library News. Other useful sites can also be found in the Internet Review Archive.
- Purdue Virtual Reference Desk
- An excellent selection of references useful to college students.
- University at Albany Libraries Reference Collection
- An extensive, well selected, and frequently updated list of resources in categories with brief annotations.
- Martindale's The Reference Desk
- A well regarded, award winning index to science reference sources. See this review from the Chronicle of Higher Education