IBM developerWorks: JFS Project
Provides specifications, documentation and downloads for implementation with the Linux kernel.
oss.software.ibm.com Details

John's Spec of the Second Extended Filesystem (ext2fs)
File structure compiled from resources published on the Internet, personal experience and Linux source code.
uranus.it.swin.edu.au Details

Simple Software Solutions: e_Fs
Provides description of features and links. Links include scenarios for use and list of efs function calls to replace standard C functions.
www.simple-sw.com Details