Here's another online vocab study tool like Quizlet or Quia. It's free and you can enter in your own data or use the data others have inputed. It already has a ton of topics in there for you to use. Once you find a data set you like (or enter your own) here are the options for studying:
You can make flashcards, do hangman, word searches... (click on picture for a bigger view)
A look at the matching & crossword puzzle features:
I like the options. You can print and edit a data set like with Quizlet. You can use this type of study tool in class or kids can use it at home. The only thing that I wish Quizlet & Study Stacks both had is a concentration (the memory card game) feature. Quia has it and my students enjoyed that the most out of all these tools. But, Quia isn't free. Well, you can use it for free, but you can't enter your own data or edit their sets. To do that you have to join. So, if the set you need is already in there, great, but if not, you will have to pay about $50.00 for a year membership. (which may be an option for you, but I mostly promote free stuff on this blog). So, I'm suggesting that Quizlet & Study Stack add a concentration feature.
Otherwise, Study Stack is still a pretty cool online vocab study tool to make things interactive & fun!