Dictionaries, etc.

Dictionary.com - look up English words, computer terms, place names, biblical names, & US ZIP codes.
yourDictionary - provides online dictionaries in 150 different languages, grammar for 70 languages, and pages of linguistic fun.
OneLook Dictionaries - allows you to search for multiple definitions of a word from a variety of online dictionaries.
Cambridge International Dictionaries - search separate dictionaries of English, phrasal verbs, or idioms.

Other helpful resources