I've tried a few times to look at the source code for various things from github or other sites, in javascript, C#, PHP, etc. I'm never able to understand the programs as a whole though. I can sort of piece together what a specific snippet of code does, but I quickly lose the context of what I'm looking at and how it fits in.

I want to be able to improve, but everything I've tried learning from so far has been too big. Where can I find well-written, but not very complex source code to look at?

edit: Sorry, to be more specific, I'm hoping for javascript/php/C#.