I just discovered this online collocations dictionary of English: Pro Writing Aid.
This was tweeted by Oliver Lawrence.
I am linking it because one of the most common searches that finds Transblawg is for collocation dictionaries.
I used to recommend the (excellent) BBI Combinatory dictionary in print, but Tom West III pointed out to me that the Oxford Collocations Dictionary for Students of English is even better (yes, I suppose I am a student of English). I now use that sometimes. Goodness, I found an online search for that at www.ozdic.com – is this kosher?