Actually, I've been recently diving into some frameworks that I've never used before, and some knowledge domains I have no experience with, and I can say that I

Actually, I've been recently diving into some frameworks that I've never used before, and some knowledge domains I have no experience with, and I can say that I've definitely used Stack Overflow to "learn". Not in the traditional sense, but almost more like an index. I'll ask "how do I do <basic concept> in <framework>", check the SO results for a well documented and thought out response (not just code snippets), and start reading. On the side in a notepad I type up the terms/concepts they talk a lot about in that post that seem necessary to understanding their post (which I do NOT usually fully understand). Then I close that tab and start learning about those concepts. Sometime's I'll also do that with code from SO - find code that works in a microcosm, and tinker on it to see what it does, look at documentation, APIs, tutorials, etc. I personally have found this to be very effective, far moreso FOR ME than a book ever could be (even a PDF book w/ searching)