Had a reference question about what free science dictionaries are online, so thought I would put some of that information up here.
tcaep.co.uk is published by scenta, in association with The Institute
of Physics, as part of a comprehensive range of websites to support
physics and physicists and others studying or working in the wider
fields of science, engineering and technology.
There is a lot of good basic information in astronomy, math, and tables of equations & constants.
This site provides links to glossaries, dictionaries,
and databases from various scientific disciplines. From the American Association for the Advancement of Science (AAAS).
From the Information Please
Almanac folks.This resource for children has an easy interface, and includes an on-line dictionary, encyclopedia, and a great games & quizzes section.