I've just started gathering the sonrise books. Just the secular ones. There is a yahoo group for secular sonrise users. They made some recommendations on books about evolution since sonrise doesn't do that. I've been getting the books either at the library or used from amazon, half.com, barnes and noble, or borders. We won't be using the instructor's guides, just reading the books that work for our family.
There is also another called
http://www.winterpromise.com/. They have a lot more options than sonlight so I was a bit overwhelmed, but they are a good resource for book titles.