Below are additional sources of information about proc file system.
Most of the best /proc/ documentation is available on your system.
/usr/src/linux-2.4/Documentation/filesystems/proc.txt — Contains assorted, but limited, information about all aspects of the /proc/ directory.
/usr/src/linux-2.4/Documentation/sysrq.txt — An overview of System Request Key options.
/usr/src/linux-2.4/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/src/linux-2.4/Documentation/networking/ip-sysctl.txt — A look at various IP networking options.
/usr/src/linux-2.4/ — Some of the most authoritative information on /proc/ can be found by reading the kernel source code. Make sure the kernel-source RPM is installed on your system and look in the /usr/src/linux-2.4/ directory for the source code.
http://www.linuxhq.com — This site maintains a complete database of source, patches, and documentation for various versions of the Linux kernel.