
When dealing with words, dictionaries are absolutely essential. Paperback editions seem to be dying slowly these days, whereas online dictionaries are confidently gaining ground. That's why I feel the need to discuss the latter ones more and mention my absolute favourites.
1. The Free Dictionary
A unique combination of precision, proficiency and style. It is very detailed, covering many fields such as Legal English, Business English, Medical English etc. Moreover, it provides the user both with an abundance of explanations and transaltions into various world languages with great precision as well, which is, according to my experience so far, a very rare thing. After you go through the definitions, check the synonims, antonims or idioms containing a word in question, you may test your knowledge by doing some exerecises provided on the right hand side of the webpage. The thefredictionary.com designers have done everything to make the user feel at home. You may customize the page yourself and thus make it suit your interests and needs, which is also a marvellous touch from the authors of the site and the whole project. All in all, A+ for this one.
www.thefreedictionary.com
2. Oxford Collocations Dictionary Online
Collocations are also an important part of the language puzzle which has to click into place if you want to achieve proficiency and fluency. Although slightly old-fashioned in terms of web pages, it is very easy to use and provides you with what you exactly need. A nice tool for translators, above all.
http://llohe-ocd.appspot.com/
3. Online Rhyming Dictionary
Good news for poets and songwriters: this website can be a useful companion while trying to shake up new lyrics or lines. Always test your choice and rewrite until you find the right combination. This tool can be more than helpful.
http://www.rhymer.com/
I am sure that there are many more online dictionaries worth mentioning, and I am sure that I will include them here the moment I come across them. By then, I warmly recommend using the abovementioned sites both for study and pleasure.