Class Central has a great listing of free online Ivy League courses from Brown, Columbia, Cornell, Dartmouth, Harvard, Penn, Princeton, and Yale. There are over 500 courses to consider. Topics range from computer science and engineering to music and history.
Carnegie Mellon University is offering a free Computer Science Course for high school students.
Amazon Future Engineers are also offering a free Computer Science Course for high school students.
Other free college courses can found on Udemy, Coursera and edX.