I got into log4net code and Nunit. Both of them gave me something to think about and taught me something new. What other aps do you know, with source code open that worth reading their code? Also, what is the best way to get into the code, sure if you can’t ask its creator a question?
A little addition: I’d like to have sources read by you and recommended in a way I read this, it is really cool and worth reading, worth digging into the code. Sure it is very helpful to know about codeplex, codeproject and other sites where you can get some code to dig into, but the question is about what do you recommend
You might also want to check out Scott Hanselman’s weekly source code discussions.
Instead of just blocks of code he takes time to discuss it in detail.