Class Tools.net. Their flash games and graphic organizers are my wiki's best friend.
If you have your students doing work or activities, have them create a timeline, fishbone, hamburger, etc. and embed it in their blog or wiki. Just copy the HTML code and paste it into the wikispaces widget or their blog.
These are so much better than the reproducible graphic organizers because they are interactive, even after being posted.
I also love using the games. Split up the vocabulary words and have each student build a game. Then, have them play each game for a set time limit and swap computers. If you split the vocab wisely, you have a fun game and you're using video games to teach.
How do you use this tool?