Once students sign up with a promo code they have 6 months of "all-access". Currently there does not seem to be a way to extend this in concurrent years without re-applying for a code and having the students sign up with a different email address.
World's free classroom. Everything you ever wanted to learn - from videos. Students can practice at this site and search the tutorials effectively. Teachers can track the students' involvement in the site here also. http://www.khanacademy.org/
Great message board application - similar to Lino and Wallwisher. Has added functionality such as post by email, chatting with participants, and polling.
Lure of the Labyrinth is a digital game for middle-school pre-algebra students. It includes a wealth of intriguing math-based puzzles wrapped into an exciting narrative game in which students work to find their lost pet - and save the world from monsters! Linked to both national and state mathematics standards, the game gives students a chance to actually think like mathematicians.