By alternatives, I mean to the traditional general biology - chemistry - physics track that many high school students follow when headed to college. Some homeschoolers, depending on their children's interests, like to do other physical sciences or focus on a specific aspect of biology. The following links are to free online courses for some science alternatives:
Georgia Virtual Learning: At this link to their Science page, you'll find courses in Anatomy and Physiology, Astronomy, Environmental Science, Forensic Science, Epidemiology, and general Physical Science.
Forensics Illustrated: Includes PowerPoint presentations, projects, labs, and tests.
DNA From the Beginning: Readings, animations and videos covering topics in Genetics.
HippoCampus: Has a number of earth science and environmental science resources.
Bozeman Science: YouTube Videos made by a high school science teacher on Anatomy and Physiology.
Astronomy - State of the Art: Beginning astronomy course from udemy.
Have you found any free science resources for high school science? Please share them in comments.