Q: Where can I find some good code examples to study and learn from?
A: Although studying existing source code is indeed a very good way of learning, it's unfortunately hard to recommend any truly good examples, because so much of the actual code out there is either pedagogical (i.e. not real-world), or all too real-world (i.e. too voluminous and complicated for mere mortals to understand).
With that said, here are a couple of links to explore:
A word of warning: there is some excellent code out there to learn from, but there is plenty of truly bletcherous code, too. If you find yourself perusing some code which is scintillatingly clear and which accomplishes its task as easily as it ought to (if not more so), do learn everything you can from that code. But if you come across some code that is unmanageably confusing, that seems to be operating with ten bandaged thumbs and boxing gloves on, please do not imagine that that's the way it has to be; if nothing else, walk away from such code having learned only that you're not going to commit any such atrocities yourself.
See also questions 18.9, 18.13, 18.15c, and 18.16.