The Brainy Bunch: The Harding Family's Method to College Ready by Age Twelve by Kip and Mona Lisa Harding. The family has ten children, are nondenominational Christians, and have homeschooled all of them.
Those who are old enough have all started college young - some as young as 10. They've graduated young and started their careers young. Overall, it's a good book. They share their own methods for homeschooling - which is actually quite relaxed. They focus on math and writing and have the children read a great deal in the other subjects. Even though the children didn't have any formal science studies before starting college, they all did fine in lab sciences.
I think it is important to note that they didn't just dump their children off at college at a young age. They started them with one or two classes and Mom was usually nearby. The Hardings endorse homeschooling fully and view their job as one of cultivating their children to be all that God has created them to be.
Their method has worked for them, and part of homeschooling is respecting others right to homeschool as they choose, and so I support their initiative and results. However, I don't necessarily think that college at 12 is the ideal. I think children learn and grow and mature at different rates. College isn't even the goal for every child. But for children who are motivated and know what they want to do in life, early college is an option (if not at 12, then dual enrollment at 15 or 16). Homeschooling is about different options and thinking about school in a different way. In that light, The Brainy Bunch adds to the conversation.