Not sure if these are cross listed on any of the sites already mentioned, but thought I'd throw in Courseara as a resource for online learning. I've done a couple of the classes and liked the format.
https://www.coursera.org/Also, this one is more specific to programming but I've been using treehouse which is a resource for mostly web or mobile app development. Edit: this is a paid subscription, but you can put your account on "hold" if you aren't going to be a heavy user. I consider this an investment because it teaches you skills to become employed as a programmer.
https://teamtreehouse.com/Another edit, I forgot Khan Academy which is a great resource for learning or refreshing your memory about math. This one is also free (like Coursera). I've only used it for math, but its got other subjects on there too.
https://www.khanacademy.org/