I like the Mother of Divine Grace School. http://www.motherofdivinegrace.org
This is a classical curriculum that is based on children’s natural stages of development. They offer a syllabus you can use to structure your day, but they make it flexible. You can join there group for the accredidation or you can go it alone. I think they even have standardized tests.
St. Thomas Aquinas Academy is also a good one. http://www.staa-homeschool.com When you join they give you a standardized test for the kids to take so that the personal adviser they asign you can help you pick the right books for your children. They also do record keeping, report cards and transcripts.
I hope this helps. I am just starting the homeschooling process.