Merriam Webster Learner's Dictionary - Type  in the word you need to look up. Click the sound icon to hear the word. 
Longman Dictionary of Contemporary English
Cambridge Learner's Dictionary    Type the word you need to look up.
Cambridge Dictionary of Multi-word Phrasal Verbs
Cambridge Dictionary Resource Page  Great resources for teachers and students at all levels.
Synonym Dictionary   Type in the word to find synonyms (other words with with a similar meaning.
Rhyme Zone  Type in a word and find rhymes, definitions, synonyms, related words, etc.

ESL Station            ESL 340 Series