In the past, we've used Horizon, Singapore, and Teaching Textbooks. We are currently using Johns Hopkins on-line for math (note: you have to apply to their program), but will probably switch back to Teaching Textbooks when we are done.
It is in video format, but my DS10 doesn't view the online lessons. He reads them and then does the accompanying problems. Once complete, he does like to put his answers in the system, because they have these little animals that morph as you get answers right and he likes to watch that process.
