Inside the Linux boot process (by Tim Jones, Consultant Engineer for Emulex Corp.) http://www-128.ibm.com/developerworks/linux/library/l-linuxboot/?ca=dgr-lnxw09LinuxBoot
GRUB loader http://www.gnu.org/software/grub/
Multiboot Specification Manual http://www.gnu.org/software/grub/manual/multiboot/
The OSkit Project http://www.cs.utah.edu/flux/oskit/
The Intel x86 Manuals http://www.x86.org/intel.doc/inteldocs.htm
Netboot http://netboot.sourceforge.net/
Etherboot http://www.etherboot.org/
Preboot Execution Environment (PXE) http://en.wikipedia.org/wiki/Pre-Boot_Execution_Environment