Stumbled across this excellent site after reading an article about it on Ewan McIntosh's Blog.
Basically it is a game site that asks children mental maths questions and how to spell words.
What I like is the competitive nature of the site, since you don't play by yourself you compete with other children on the site. The children score points based on how well they do, what is great is that you can play children from all over the world, basically anyone who is logged in.
The site is very secure the only information you see is the login that the children use. The site itself collects only a very small amount of information about the child, date of birth and country. If you create a school account the children will need that as well or they just put in their parents email address and within 7 days their parents must respond or the account is frozen.
The school account allows you to track those in your class and see what games they have been playing and how they are doing.
This is a very interesting alternative to using DS's and Doctor Kawashima's Brain Training. Next year I will be looking into this in more detail.
Check it out.