Just wanted to toss up a quick post directing attention to a cool little website a friend pointed out to me: FreeRice.com.
The schtick is that you define words, and for every one you get right, 20 grains of rice are donated to the United Nations World Food Program. It gauges how many words you get right and determines your vocab level, giving you words slightly above that level.
Of course, you can read all about the details on the website but definitely check it out. Improving my vocabulary AND helping a good cause? Sign me up!