First of all, I got a notice from Learn Zillion indicating that they have expanded their website to include a K to 8 Math Curriculum that is an open cloud based curriculum, great math videos, reading and writing lessons. I use the videos all the time in my classes because they are short, to the point and they talk about misconceptions. I absolutely love the videos. The other thing is that it is all free. That is awesome!
The other thing is using SAS's gloss app. I had a student today who worked all his multi-step equations out on the whiteboard choice before writing it on the paper. If he made a mistake, he just undid it and tried again. It was absolutely wonderful. My students are beginning to use it as a whiteboard so they can make mistakes.