I found this site and BOY! am I addicted.....for a good cause of course. You don't think I would just spend time on a site showing off my vocabulary skills and marvelling at all those new words I learn, unless there was some good coming from it, do you?.
Free Rice donates 10 grains for each word you get right - go ahead - feed someone while you feed your mind.
My best word learning so far has been "hardtack".