- Dictionary.com allows you to search multiple dictionaries and references at the same time.
- Dictionary.net returns word and phrase definitions from a variety of English dictionary resources
- iTools has links to a number of dictionaries, thesauruses and other language tools, including online translators.
- Merriam Webster Dictionary
- LookWAYup Dictionary/Thesaurus and Translation is a large online English dictionary that tolerates small spelling errors (U.S. or international spelling), shows definitions for multiple senses of the word and for each sense shows synonyms, related terms and usage examples. It will also translate words to French, Spanish, Portuguese, Dutch and German or vice-versa.
- Online Dictionaries
- A list of biographical info at Biographical Dictionary
- The Visual Thesaurus offers a visual way of exploring the relationships between words.
- Bartlett's Familiar Quotations
- Robert Harris has a searchable rhetorical devices handbook and a glossary of literary terms.
- Voice of the Shuttle is a massive humanities database portal.
- Paul Brian's Common Errors in English Usage has an extraordinarily comprehensive list of errors in English usage and advice for how to avoid them.