Wordia.com

This is a great site, but I'm not sure how useful it will be for any but extreeeeemly advanced learners.  It's a dictionary site with a twist - people choose a word and descibe it in short video clips that they upload.  Some of the words are useful, like 'kindness' and 'nonsense', but most of them are words that most native speakers might struggle with.  It's a lovely, interesting site (and the listening practice might be useful), but if you direct your learners to it, make sure they know that the words are pretty low frequency!  My favourite is 'fermana' (uploaded by a rapper/ comedian called Doc Brown).  No, I didn't know what it was before either, but I do now - have a look and find out yourself!