There seems to be a durge (if that's the right word) of web servers called "Tiny Web Server", all vying to be the smallest web server. And now there's another one! I don't think it's the smallest, but it is a full web server for delivering static pages and documents.
It's written in Java, and the source comes to 23K. It should be pretty easy to extend to make it write dynamic web pages, so it should be ideal for starting your own web server project, or just giving you an idea of how web servers work. Or how not to write code. Take your pick.
It's available via SVN here. (That's svn://www.onlinegameplanner.co.uk/TinyWebServer).