As part of a class and just for fun I would like to write my own .zip file encoder/decoder. Including handling the encryption/decryption. The problem I am having is finding a good document that explains the .zip file format. Does anyone have any resources that describe how it is structured? Particularly for the header? I have found a few papers and things that give parts of the header, but none go in depth on the different values for the fields and what the correspond to. I remember a while back there was a site that had commmon file types and descriptions what they were. I know the .zip file format is pretty much what some games (ie quake) use, so I'm sure there is info out there. Does anyone have some good resources?

http://www.wotsit.org perhaps? Hosted by GameDev!

Wow, I was gonna suggest that. I didn't know it was hosted by gamedev though.
You've got a lot to do I imagine. Good luck!