There are two great web 2.0 tools today I am going to talk about the first is to create animations in the math classroom. You make small animations, it is very easy to use and you can create flash-style animations. You can post your animations to YouTube, Facebook, and even a blog. There are pre-made clips where you can reuse them. I created one at http://www.doink.com/ it was fun and for students in your classroom you can use this to post about questions or even solve questions.
pi and i by treverreeh, made at DoInk.com
The second web 2.0 tool over animation is http://gickr.com/ and it lets you instantly create animated GIFS online and for free. Just upload pictures and create funny flashy slide shows with you and your friends, cartoons, previews, banners, etc. Post them anywhere you can post pictures. It is simple to use and fun for your students to create small videos. There is even a gallery to show them to other people.
Using these two tools in your classroom will help engage students and learning math more fun.