There are a variety of online websites and resources for free online homeschool curricula. These include Kahn Academy, LessonPathways, MIT and CK-12. They have lessons and curricula for students of all ages and home educators of all experience levels.
Khan Academy provides interactive lessons and videos for students from Kindergarten to 12th grade. The program is self-paced and includes math, science and history lessons with 10-minute video clips to help students grasp difficult concepts.
CK-12 offers a full curriculum for students with lesson plans on every traditional subject. This is also a self-paced program that allows the students and home educator to choose what they want to learn each day while also providing a concept map of the recommended schedule to make learning new concepts easier. There are also many textbooks available for free download.
LessonPathways is a more structured program, providing a different pathway of learning each week with pre-planned lessons and topics. Though each grade does have its own pathway to follow, the educator can add, delete or change pathways to fit their student's needs.
The program from Massachusetts Institute of Technology is geared towards students in grades nine to 12 and includes study guides and courses that prepare students for AP exams and college coursework.