I just wanted to let everyone know about a science program I'm considering for a high school science class. It's called Global Systems Science and you can get more info at http://www.lawrencehallofscience.org/gss/.
You can download and printout all the teacher guides for free and view the student texts for free. The cd with the entire program is only $20. I've ordered it to take a closer look at the program to see how we might use it in our co-op. From what I've seen so far, this curriculum could easily be used by homeschoolers.