DiddyFtpServer is a very simple Ftp server library written in Cocoa/Objective C that you can include into your projects to add file access.
The latest version can be found in SVN. Currently this is in the form of a project which compiles a static library and then creates a demo app using the static lib.
It supports a subset of Ftp Commands. You can upload and download files and list the contents of a folder.