The World Fact Book
Encyclopedia of Mathematics
The Math World
Internet Encyclopedia of Philosophy
Stanford Encyclopedia of Philosophy
Ancient History Encyclopedia
An Encyclopedia of World History
The New Palgrave Dictionary of Economics
Encyclopedia Astronautica
Encyclopedia of Earth
Science World
Encyclopedia of Biology
FOLDOC (Free Online Dictionary of Computing)
WeboPedia
Encyclopedia of Cryptography and Security
McGraw-Hill Encyclopedia of Science and Technology
Gale Encyclopedia of Genetic disorders
Analytical Chemistry
Encyclopedia of Life
Medline Plus: Medical Encyclopedia
The Plant List
Flora Europaea