Continuing with the vocabulary idea, FreeRice.com is an amazing site that not only teaches students new words, but also feeds the hungry through the UN World Food Program. Study vocabulary and help end world hunger at the same time!
I have used this site in the classroom to encourage students to prepare for the state assessments, the PSAT, and the SAT. It is a learning game, which means that the words get harder each time you get an answer correct. By creating a login, you can track your progress and compare your abilities to other members of the site.
Teachers can create a classroom group and let students face off against each other to earn rice and learn vocabulary. The students really get into it to see who is the "wordiest".
The site also quizzes on other topics than English vocabulary. You can feed the hungry and quiz yourself on art by identifying artists of famous paintings, chemistry symbols, geography where you identify countries on a map, and more.
And Leslie, this one has Spanish vocabulary!! You can have your kids practice with this site, even if they can't get on Visuwords!
Check it out here: