Several years ago, when investigating homeschooling, Paul and I attended a homeschool conference in a nearby state. This conference (as I imagine with all) had a huge vendor hall for business to hawk their wares. It's a great resource to see and touch books, games, and curriculum before purchasing. Often, too, the conferences have discounts available during the length of the conference.
I remember the Teaching Textbooks booth catching my eye. The cover illustration and look of the math curriculum was a lot different than anything else I'd seen. As we were just preparing to homeschool a 5 year old, though, I was pretty sure I could handle the math material I was preparing to cover with Jack.
Then a friend mentioned the company again to me last summer and I decided to check it out. Since fall, now, Jack has been covering their "sample lessons" on their website. He worked through maybe a dozen for level 3 & 4. It's been a supplement to his regular daily math and a fun way for him to end the week doing math on the computer (which while still learning, is SUPER FUN when done on the computer, apparently).
Each lesson has a short lecture, followed by sample problems and then 20 or so math problems to work through. The lecture and problems are very interactive and engaging. You can find a better description of it at their website, of course.
I recently purchased the Math 5 cd rom set with workbook. Seeing it now, I'm not sure we'll use the workbook for Jack, but at least we have it for follow up with him or the other kids. As the others grow into higher math, too, they'll be able to be added to the cd-rom set without having to purchase anything extra. It was the priciest item I think we've purchased thus far at just over $100. There are over 100 lessons, though, so he'll be working through it for sometime.
I’ve read many reviews for this and other texts on line, and while this one is reviewed as a basic math (like this set isn’t going to grow your kid into a math whiz) it is well used in the elementary years and a good price compared to others out there, as well.