Vocabulary University--This site groups words according to topics. You can register (it's free) to enter the site. It contains many games, puzzles, etc.
Links provided by the CALL Lab at Ohio University.
Concordance Use this site to look for many examples of vocabulary words in context.
Co-Build Dictionary Search for words on-line; search by letter, search by picture, grammar, pronunciation
Thesaurus--see the connection between words. This one is magical.
On-Line Dictionary This web site transforms any webpage into links to Dictionary or Thesaurus lookups.
Mono-Conc Companion web sites. This site contains links to sites that concern using concordance software for gathering data about language.