- Merriam-Webster Collegiate Dictionary - red audio icons next to an entry word can be clicked to hear the word pronounced by a real voice.
- Visuwords - Look up words to find their meanings and associations with other words and concepts. Produce diagrams reminiscent of a neural net. Learn how words associate.
- Wiktionary - a sister to Wikipedia
- Information Please Almanac
- My Virtual Encyclopedia
- Reference.com encyclopedia
- Smithsonian Institution Libraries - digital library
- World Encyclopedia
*Notice Wikipedia is not listed here.
- Encyclopedia of Life
- Gale Virtual Reference Library - 37 science encyclopedias and many more on other subjects
- Oxford Reference - 48 science encyclopedias and many more on other subjects
- Science in Context delivers integrated content through 150+ comprehensive reference sets
- Today's Science
Need more reference sources?
Subject Guide to Online Reference Sources
- Arts & Humanities (see also: English & Literature and History)
- Business (see also: Economic Statistical Sources)
- Encyclopedias & Almanacs
- English & Literature
- Government & Law
- Health, Medicine & Nursing
- Maps and Atlases
- Readers Advisory
- Statistical Sources
Still not finding what you need? Try Virtual Reference Shelf from the Library of Congress.
There are plenty of ways to get help when you're stuck!