I've been doing this for a year, and it's the most helpful learning technique I've found in 14 years of computer programming. I didn't go to school for it. I just learned by necessity because I started a website that just kept growing and growing, and I couldn't afford to hire a programmer, so I picked up a few books on PHP, SQL, Linux, and Apache, learned just enough to make it work, then used that little knowledge for years. But later, when I worked along side a real programmer, I was blown away by his vocabulary! We were using the same language, but he had memorized so much of it, that I felt like a child next to a university professor.