Freerice offers a fun way to improve your vocabulary and help others. Take a vocabulary quiz and help feed the hungry. In their own words,
For each word you get right, we donate 20 grains of rice through the UN World Food Program to help end hunger.
AidToChildren is similar. You take a vocabulary quiz and for every word that you define correctly, one fourth of a penny is donated to this organization.
In their own words,
AIDtoCHILDREN was developed based on a desire to help under privileged children in the most impoverished places around the world.
Have fun and make the world a little bit better.