This entry is going to break format in many ways.
Here is a variety of site that offer to teach you something. Most are entirely free, although they will hit you up for a donation now and then. There are hundreds (if not thousands) of these, so if your favorite isn't listed, please accept our apologies. The Doctor only has so much time to surf and write reviews...and these days he prefers the former.
duolingo.com - learn a language in five minutes a day
khanacademy.org - Math, Science, Finance, Music - it seems that Khan Academy intends to become Khan University!
codecademy.com - learn to program in just about any computer language
w3schools.com - another programming site, but with all emphasis on web-based tech
lynda.com - video training for design, photography, programming, business and more
We hope these give you a start on a career, a career change, a hobby or a fun way to stay out of trouble on rainy days.
If you'd rather read random content and not worry about "learning" per se, you can go to Wikipedia.org's Random Article link and find something interesting....weird!