OneLookhttp://www.onelook.com/
Wordnikhttp://www.wordnik.com/
Forvohttp://www.forvo.com/
Dictionaryhttp://www.dictionary.com/
Thesaurushttp://www.thesaurus.com/
Cambridge Onlinehttp://dictionary.cambridge.org/
Free Dictionaryhttp://www.thefreedictionary.com/
BNChttp://corpus.byu.edu/bnc/
COCAhttp://corpus.byu.edu/coca/
CCEhttp://www.lextutor.ca/concordancers/concord_e.html
Wiktionaryhttp://en.wiktionary.org/wiki/Wiktionary%253aMain_Page
Wikipediahttp://www.wikipedia.com/
Purdue OWLhttp://owl.english.purdue.edu/sitemap/

Dictionaries:

Corpuses & Other References:

(pronounciation)

EL&Uhttp://english.stackexchange.com/questions
Online Etymologyhttp://Etymonline.com/
Ngramshttp://books.google.com/ngrams
Phrase Finderhttp://www.phrases.org.uk/
ODOhttp://oxforddictionaries.com