Additional Resources

Below are additional sources of information about proc file system.

Installed Documentation

Some of the best documentation about the proc file system is installed on the system by default.

/usr/share/doc/kernel-doc-<version>/Documentation/filesystems/proc.txt - Contains assorted, but limited, information about all aspects of the /proc/ directory.

/usr/share/doc/kernel-doc-<version>/Documentation/sysrq.txt - An overview of System Request Key options.
/usr/share/doc/kernel-doc-<version>/Documentation/sysctl/ - A directory containing a variety of sysctl tips, including modifying values that concern the kernel (kernel.txt), accessing file systems (fs.txt), and virtual memory use (vm.txt).
/usr/share/doc/kernel-doc-<version>/Documentation/networking/ip-sysctl.txt - A detailed overview of IP networking options.

http://www.linuxhq.com/ - This website maintains a complete database of source, patches, and documentation for various versions of the Linux kernel.