This is one of the BEST math sites I have found! I use it with my math intervention students. It gives very detailed data on each of the kids!! I have used it for a large portion of this school year! Best thing...IT IS FREE!
Link that follows leads to a brief article that describes the program. Did I forget to mention that this resource is free! http://myclasstech.com/2012/02/06/tenmarks-21st-century-math-instruction-has-arrived/