Dictionaries
I was asked the other day about good English dictionaries, so here are a couple of recommendations, with links to Amazon:
Longman Dictionary of English Language and Culture. A personal favourite (and I need to buy another one - mine has fallen to pieces).
Longman Dictionary of Contemporary English. Another great dictionary from Longman.
The Oxford Advanced Learner's Dictionary is an excellent dictionary from OUP.
The Macmillan English Dictionary for Advanced Learners is another of my favourites - a really good advanced learner's dictionary. And I know the general Editor, Michael Rundell, too!
Finally, don't forget Michael Swan's Practical English Usage, a wonderfully clear reference to how English works.