I have set up a social network (ning) for gifted math students across our school as an action research project with great results. One of the key sites i used was http://www.mathplayground.com/mathtv.html the kids loved this site and the videos were a great way to scaffold their new learning. Their task was to articulate their solutions using 'smartrecorder' and then uploading this to the ning. Students would peer comment and the discussion was great, especially when they solved problems a different way. After this the kids had to write their own problem of a similar context and send this to all the members in the network. It is a great program which I hope to be able to continue in the future.
Some of the difficulties were time as I ran this on top of my own class and was often replying to emails late on Saturday nights with kids asking for new questions etc (How fantastic is that!).
This is a game with a mythological theme. Students use certain math skills/concepts in order to progress. My collegue uses it (she has less internet restrictions at ther school) and her students are begging her to teach them higher skills in order to advance in the labyrinth. Students can play at home and on-line with each other.
Feel free to explore my educational resources site and place the link on your school's computers. From the main menu click on "Math" followed by your topic of choice. All the links are visual which makes it easy for kids to access. Click on the address below: