MathWorld
- Glossary of terms. Material ranges from undergraduate to research level.
- http://mathworld.wolfram.com/

Kyoto Encyclopedia of Genes and Genomes
- Current knowledge of molecular and cellular biology in terms of the information pathways of interacting molecules or genes and links from the gene catalogs produced by genome sequencing projects.
- http://www.genome.ad.jp/kegg/

Encyclopedia Mythica
- Over 6,000 entries on mythology, folklore, and legend. Includes some images and stories.
- http://www.pantheon.org/

Encyclopedia of Trotskyism On-Line (ETOL)
- A resource center for the study of the international Trotskyist movement.
- http://www.marxists.org/history/etol/index.htm

EngineersWorldwide.com
- Worldwide directory for the design, engineering and construction industries.
- http://www.engineersworldwide.com/

The Book of Threes
- Read and contribute on the both natural and unnatural occurrences or the number three.
- http://www.threes.com/

Peakware World Mountain Encyclopedia
- Includes reference information such as height, location, first ascent data, photos, web links, summit log entries for hundreds of mountains worldwide.
- http://www.peakware.com/

Virtualsources.com
- Find information on every country in the world. There are massive amounts of statistics on everything from population to a country's legal system.
- http://www.virtualsources.com/

The Satellite Encyclopedia
- The Satellite Encyclopedia contains fact sheets with basic information such as launch date, country of origin, official identification, and payload description (EIRP maps). Extended launch vehicle section. Future satellites descriptions. Over 4000 pages a
- http://www.tbs-satellite.com/tse/online/

Tallship Fan
- Encyclopedia of sailing ships online: data, photos, history, contact addresses and other information about traditionally rigged sailing ships.
- http://www.tallship-fan.de/index_e.htm

Creation-Evolution Encyclopedia
- Over 700 printed pages of material discussing the controversy between creation and evolution.
- http://www.pathlights.com/ce_encyclopedia/Index.htm

Natural Remedies Encyclopedia
- Natural Remedies for over 500 diseases, such as cancer, heart disease, sexually transmitted diseases, childhood diseases, with a special section on preventive health.
- http://www.pathlights.com/nr_encyclopedia/

Cyclepedia: Motorcycle Information
- Motorcycling information, repair manuals, technical data, and useful statistics organized by manufacturer. Completely searchable and easy to use.
- http://www.cyclepedia.com/

Encyclopedia of Life Sciences
- Originally commissioned and peer reviewed articles across the life sciences. Online encyclopedia requires paid subscription.
- http://www.els.net/

Encyclopedia of American Silver Marks
- This site contains identification of marks of American Silver Manufacturers including Gorham, Tiffany, Towle, Duhme, Wallace, Lunt, and Watson. All marks are clearly illustrated and include a short history of each company. Links to other silver collecting
- http://www.edensterling.com/silvermarks.html

Encyclopedia of Canadian Theatre
- Thorough coverage of present and past theater news and productions.
- http://www.canadiantheatre.com/

Storm Encyclopedia
- Covers the basics about severe storms with notable examples of Mother Nature's ill-tempered handiwork.
- http://www.weather.com/encyclopedia/