I found a really cool site!
The site is called Wizcabulary. Not only is it a site to help students practice vocabulary, for every question answered correctly, the company donates money to an organization that buys graphing calculators for students who cannot afford them! As a result of my three classes working on this site, our classes contributed almost $25.
I had the students set up accounts using their Achieve login information. I had them enter my Google e-mail address as the parent address. The parent address is used so a parent can incentivise his/her child's usage. For example, when the child earns three trophies, an e-mail will be sent alerting the parent. Maybe the child gets a reward of some sort. I am going to make a display in the room with the highest achievers. Try it out. See you you do. (I challenged my 16 year-old daughter. If she gets five trophies, I will give her $10. It is work, but this is studying that will pay off.)
Oh, there was plenty of giggling in class. I do teach middle school children. Let me explain. As you earn points, the yellow dude you see in the picture gets clothes. If you get one wrong, he loses one piece. That would not be my choice of how to represent achievements, but it is what it is. Why not earn coins or flowers or... anything other than clothes? I told them to think of him as wearing long-johns.