Linux Kernel Commentary - Contains a set of documentation on how parts of the kernel work. www.cse.unsw.edu.au/~neilb/oss/linux-commentary
The Linux Kernel - Online book about the principles of the Linux kernel, including memory management, interprocess communication, device drivers, and the file system. sunsite.unc.edu/linux/LDP/tlk/tlk.html
The Linux Kernel - Open source book on the Linux kernel. kernelbook.sourceforge.net