Catholic Encyclopedia
An encyclopedia related to matters involving the Catholic relision. This is a broad area, with much historical and biographical information about many, many related things.
An online encyclopedia that covers technology and all things related to computer technology and the Web. Very thorough and complete, with links back and forth between many concepts and topics.

Britannica (Free Version)
The free version contains advertising and is pretty busy, but worth a visit due to the high quality and selection of Web links.
Encarta Encyclopedia (Free Version)
This is a scaled down version of the commercial version, but still worth checking if you don't have access to a full version.
Encyclopaedia of British History
A wonderful historical encyclopedia created in Great Britain, and made freely available on the Web by Spartacus Publishing Company.
HyperHistory Online
"HyperHistory presents 3'000 years of world history with a combination of colorful graphics, lifelines, timelines, and maps."
Infoplease Encyclopedia and Dictionary
A combined small encyclopedia and dictionary.
LetsFindOut Kids Encyclopedia
If the other encyclopedias are over your head, you may want to give this one a try, designed for the younger student.
Time-Life plant Encyclopedia (The Virtual Garden)
"Looking for a plant, houseplant, tree, or shrub? This searchable database contains almost 3,000 species selected for general use in North American horticultural practice."