Have you guys heard of Linguee?
It's like a bilingual dictionary, but better, since it not only gives you the word you are looking for, but also has translated excerpts to show you how the word would be used. I found it very useful when I'm doing my Portuguese homework, since there are not too many Portuguese-English/Spanish dictionaries out there.
Yes, I mention it here along with several other online dictionaries: https://www.duolingo.com/comment/594701
If you like http://www.linguee.com you should try http://context.reverso.net/translation as well. Its database seems to be created from less formal sources than Linguee. It used to include many swear words taken from film subtitles but it seems more tame these days. Also have a look at the multilingual sentence database at http://tatoeba.org/
I don't like using wordreference as much, mostly because the Portuguese dictionary is still under construction, so it doesn't have all the words I'm looking for. Also, at least in my experience, some of their example sentences for the word are in English, and that doesn't really help me. Wordreference in Spanish is great though.