Oak Meadow language arts was a link sent from my friend Kendal over at Field Schoolers (she doesn’t use Oak Meadow but is an experienced Montessori teacher who knows oh so much about curriculum). It has some great reading choices. There’s even a common core supplement for those who want it or need it for state compliance.
The Lukeion Project – ages 10 and up – classical courses for middle and high school
Build Your Library – full year secular homeschool curriculum for 9th grade.
Edx.org: free high school courses (including AP). These are worth a look.
SAT Prep – Terrible site name but reasonably priced test prep material that I’ve seen recommended in secular homeschool groups.
PrepScholar – highly recommended test prep online. Reviews for this site are really good.
AP Homeschoolers – AP Online classes