I don't think reading another game's source code in isolation is going to help you learn much; there's a pretty severe lack of context in most code, so you won't know why particular programming design or implementation decisions were made. You can very easily pick up bad habits or the wrong idea.
That said, a similar question has been asked here beforeimilar question has been asked here before. Also, here is a list of open source games from Wikipedia, and this website is dedicated to open-source game development news and you might be able to find some examples there. Beyond that, it's a little difficult to provide what you've asked for since you haven't offered very many guidelines as to what you're trying to learn.
