Macmillan have just put their advanced dictionary online for free.
It has all the usual dictionary things - definitions, examples, phonetics, frequency info - plus sound files of pronunciation, thesaurus and lots of other good stuff.
I'm sure you already knew about the Cambridge online dictionaries, which gives you access to five dictionaries: advanced, learner's (intermediate), idioms, phrasal verbs and American, but no sound files.
David
