e-Learning for Kids online courses in math and other subjects, too!
I've also found some great interactive lessons and activities on BBC School's Bitesize site.
There are also some demo lessons on the Time 4 Learning site.
I've used some of the demo lessons on the Math Upgrade site.
For skill practice, the IXL site may be useful, or head over to Mr. Nausbaum's site for some great math games!
There are a ton of math sites here. I admit I have not gotten around to exploring them all, but I'm sure you will find something that your students will like.