5. MIT Open Courseware
If you always wanted to attend a big-name school like the Massachusetts Institute of Technology, now you can do the next best thing by taking many of its courses for free from your home on your own time.
The MIT Open Courseware site posts course materials from a wide variety of classes you can search by department.
Choosing a course will show you when it was originally taught and by whom, and will give you access to the syllabus, course calendar, readings, assignments and study materials.
You can download the course materials and work through the course at your own pace.