I found the neatest information and wanted to share with you. In doing some research on hobbies, I found that most colleges, such as MIT, post their past courses online for FREE. Yes, you can take a course from MIT, with all the notes, slide shows, tests and everything for FREE! Some of the classes that I looked at needed a text book which you could purchase through Amazon.com for very cheap. For the class I was looking at the books would have cost $12 and $8 of that was shipping costs.
There are courses that you don't need to purchase textbooks for or that have all the information right there online.
I was amazed at the course catalog for MIT and other notable universities! Of course, you are not getting credits for taking these classes but if you ever wanted to know about Astrodynamics or linear algebra, here's your chance! I know I'm going to be checking out some of the courses, I just haven't decided which one first.
Here are the websites that I've found so far:
Online Education Database: http://oedb.org/library/beginning-online-learning/200-free-online-classes-to-learn-anything/
Free Online Classes and Online Courses http://www.guidetoonlineschools.com/articles/tips-and-tools/online-classes
Lots of choices of things to learn and who knows where it might lead!