Below are additional sources of information about proc file system.
Some of the best documentation about the proc file system is installed on the system by default.
/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 detailed overview of IP networking options.
/usr/src/linux-2.4/ — Some of the most authoritative information on the /proc/ directory can be found by reading the kernel source code. Make sure the kernel-source RPM is installed on the system and look in the /usr/src/linux-2.4/ directory for the source code.
http://www.linuxhq.com/ — This website maintains a complete database of source, patches, and documentation for various versions of the Linux kernel.