I put together a US History Course for my 2 boys and as a number of my friends asked for it, I have 'prettied' it up and made it available as a download for anyone who wants it. Both mine took the AP US History exam after doing this, but I was more focused on giving them the best course possible (ie interesting and thought provoking and enjoyable) than I was to 'teach to the test' - so don't be put off if you aren't interested in your kids doing that. You do need to get the resources I used, but many are available in pubic libraries (that's what I used as much as possible). I also added in lots of movies - so even if you use another history course you might like to see my movie suggestions. Here is the blog post where I describe it - and the download link can be accessed from there http://fundafunda.com/blog/in-depth-us-history-course-for-high-schoolers.html
From what I read, the schedule is free, but the lady centered her study around a curriculum that she says on the resources list you should not pay more than $500 for. Hopefully I misunderstood or the amount was a typo. If anyone has looked into it, and I wrong, please correct me.