Over the summer, I bought a set of books from a college student selling door-to-door. They're called Explore and Learn. There are 6 volumes about the human body, the history of civilization, space, technology, nature, and a world atlas. They come with a cross-curriculum list - detailing the science, math, language, etc. in each book - and a large wall map. I didn't buy them to use as a standard curriculum, but they could certainly be used that way. I just keep them on the shelf and the kids get them out at least once a week to read them. I love these books and at $100 a set, it was a very good investment. The company that publishes this series also sells software, audio cds, a large set of encyclopedias, and a fabulous set of K-12 (and beyond) everything-you'll-ever-learn-in-school kind of books. A homeschooler could build curriculum until their kids move out of the house with these books.
The problem is they only sell their books through college students door-to-door. Just like any other exclusive company like Avon or Mary Kay, you can only get the products through a "representative." Unfortunately, unlike Avon or Mary Kay, there is no way to locate a representative because since its a summer job to earn money for college expenses, the salespeople change every year and are only available in the summer. I plan to continue to check their website, just in case they do list contact information in the summer.