This website was widely circulated awhile back but I came across it again the other day and made it a goal to return to it once a day. I don't know if I just didn't realize it before or it's a new feature but you can change the subject matter of the questions. Instead of vocab, you can quiz yourself on Spanish vocab, chemistry symbols, English grammar, geography, famous paintings, French vocab and even multiplication and algebra. What a great way to learn AND give back. For each right answer the project donates 10 grains of rice to the UN World Food Program to help end hunger.