Online dictionaries are no longer the future, they are the present. They all have a beautiful feature: you can listen to the words you are looking up. So, there are no excuses for wrong pronunciation any more. Check these out:

 

Macmillan dictionary

Apart from the obvious, Macmillan Dictioanry has a "blog" with interesting articles; a "Buzz word" section that showcases words that are fashionable or trendy; and an open dictionary, created with the help of everyone.

Oxford Learner's dictionary

One thing I love about the Oxford dictionary is the section devoted to "topics". They have grouped words that belong to the same areas, making it extremely useful when you are writing a composition, for example.

Cambridge Dictionaries Online

A very comprehensive dictionary that includes the level (according to the Common Reference European framework) to which a word belongs, i.e., A1, A2, B1, B2, C1 or C2.

The Urban Dictionary

If you want to know about slang, or informal English. Or words that are so new that haven't been included in other dictionaries yet, this is the place for you.

Wordreference

And of course, the Wordreference may come in handy if you need to look up a word in Spanish for a translation. But be careful, translations are sometimes too general. You should always double-check with a monolingual dictionary after you find your word.

TED: Ideas worth spreading
TED stands for Technology, Entertainment and Design, and it is a set of conferences that started to run in 1990. You can find entertaining talks about anything and everything. They are interesting, fun and inspiring. You can hear different accents and you can switch the subtitles on if you need them. Highly recommended!

Ororo.tv
A website where you can watch tv series and movies in original version. You can also set the subtitles (in English) and, the most amazing feature is that you can vary the speed --so, if there's something you are having trouble understanding, you can slow the video down. Watching tv series is free, but the time each day is milited. Some movies are free, some others you have to register and pay.

BBC Learning English
This website is being developed, which means that you may find new features shortly. Right now there is a lower intermediate course and a higher level (features), for intermediate / upper-intermediate students. Among these features you will find "Word in the news" and "Six Minute English", as well as a Pronunciation section and a current vocabulary area (The English we speak).

LearnEnglish / British Council
Games, stories, listening activities and grammar exercises. There is even an IELTS exam practice section.