Today I learned something.
Today I learned that a Stack Overflow is not just a good place to go when you're stuck with something or you want a second opinion. It's also a good place to go when you want to learn something.
Here's how to do it.
Go over there, and look for recent questions on the topic that you want to learn something about. Preferably questions that are not exactly completely answered, and that are non-trivial to answer. But, try to stay away from the "please do my homework for me" type of questions.
You don't have to have an answer ready for it. I usually browse SO and sometimes find answers that I can just type from the top of my head and be done with it. But that's not what I'm aiming for here. Try to find a question where you know you'll spend a good 15 minutes to half an hour figuring out what the real answer is, and then try to answer it. Ideally, you'll have an understanding of the problem, but you just know that if you spend some time, you'll come up with a really good answer.
You'll spend 15 to 30 minutes on it, because you'll have to do some research and you'll have to make some sample code (and test it too!). You don't need to write out an entire application. Sometimes it's enough to have a couple of lines of code in your answer that will do the trick, but you'll need to make that test app for yourself to make sure that what you write will work.
Don't be a rep whore. You won't gain much reputation points, because it may be an older question (older than 2 minutes) and the person who posed the question may have left permanently, or there may be less complete answers that have already been accepted. But the point it not to gain rep. The point is to learn.
That's what I did today. It took me little over half an hour. But I learned something. And I'm gonna do it again tomorrow.