Commonly Misspelled Words in English - Select a reference source and click on any word in a list to get a definition, pronunciation or translation of that word to your language. Take a quiz on spelling.
Daily Vocabulary Test - A new short three question multiple choice quiz every day to test your vocabulary knowledge.
Dave's Choice Words - Dave's Choice Words are fun, free vocabulary building exercises.
Exploring Words - Another advanced English-vocabulary program for long-distance learners of all ages, everywhere.
Grandiloquent Dictionary - A collection of 2000 words which are often omitted from dictionaries, and are in danger of being eliminated from the English language.
Heenan's Universal Dictionary - A collection of weird and wonderful words and their alternate meanings; sources, too, where available.
International House of Logorrhea - An online dictionary of obscure and unusual words and obsolete terms to help enhance vocabulary; over 15,500 English words with brief definitions.
The Phrontistery - A site for lovers of obscure and unusual words, featuring a dictionary of rare words, word lists of vocabulary on specific topics, essays and discussions on etymology, vocabulary and language usage.
Vocab Vitamins - Introduces an uncommon word or phrase each day, along with a definition. Includes archives, and a daily email service.
VocabularyMail.com - A free daily email broadcast of one to three words, their definitions, and explanations and examples of how to use them effectively in your speech and writing.
Vokabeln.net - Web-based vocabulary trainer with a multilanguage interface. Features shortcuts for special characters used in ~100 languages.