As I’ve written before, I believe that one of the best ways of becoming a master programmer is to study the work of the masters. One of the best sources for this that I know of is the BSD Unix sources. Years ago I purchased a CD with the code for all the BSD releases. It was a great resource and I learned a lot.
The other day, I came across a link to an online SVN repository of the same thing. This is also a great resource. Of course, it’s mostly of use to C programmers or those that want to be. If you’re doing front-end work in Ruby, or JavaScript, or some other higher order language you may not be interested. If you want to find out how the Web and operating systems really work, it’s hard to imagine better material to study.