Online Reference Materials

Encyclopedias

• Bartleby a good selection of many types of reference materials
• Encyclopedia.com includes The Columbia Encyclopedia,
  Oxford's World Encyclopedia, and Encyclopedia of World Biography
• Gray's Anatomy

Dictionaries

• Merriam-Webster--Hear the words, use the thesaurus, find roots and meanings
• Dictionary.com--Covers basics of English, plus some other languages
• DictSearch--All-in-one language dictionary translator

Thesauri

• Visual Thesaurus--a visual representation of word associations, requires Java plug-in

Almanacs, Factbooks, and Gazetteers

• Old Farmer's Almanac--the original American almanac, including phases of the moon, weather predictions, and other assorted farmer-based sundries
• World Factbook--the definitive guide to world statistics, maps, and other country-specific information

Maps

• Mapmachine--overlay geopolitical, topographical, and other data maps on one another
• Mapquest--used by many for finding driving directions
• TopoZone--from the makers of Topo maps