DICTIONARIES

Here you have some examples of good dictionaries online:

1. WORDREFERENCE (it's not only a bilingual dictionary, but also monolingual and a forum with questions and answers)
   
2. REVERSO (translation of expressions, definitions, synonyms...
3. CAMBRIDGE (with interesting resources)
4. MERRIAM-WEBSTER (famous dictionary, with very interesting resources, esp. for advanced students)
5. OXFORD COLLOCATION DICTIONARY (a dictionary to show which words can go with the word you search)
6. LINGUEE (a dictionary to see expressions in texts in the original language and the target one)