I've become...not addicted to, but interested in, FreeRice.com It's a online vocab game where for every correct definition you guess, ten grains of rice are donated for the United Nations to distribute. As you play and make correct guesses, you get harder and harder words. Pretty awesome.
Here are some of the examples of why you should play FreeRice:
autarky - self-sufficiency
pulchritude - beauty
frigorific - chilling
terpsichorean - dancer