No matter where you live, how old you are or how much money you have, as long as you have internet access you can now attend high quality university-level classes for free and at your own pace. The following 3 providers offer complete courses, including lectures, reading material, tests, assignments and exams, and even certificates of completion, all for free.
Udacity is definitely the most user friendly. Courses are mostly in computer science, with also some in mathematics and physics. 19 courses are available for now.
Coursera has the largest selection with a total of 210 courses so far, in many disciplines including biology, computer science, engineering, business etc.
EdX is a more recent collaboration between MIT and Harvard to offer the best courses in every discipline. So far, 15 courses are available.