http://www.gnu.org/software/grub/ — The home page of the GNU GRUB project. This site contains information concerning the state of GRUB development and an FAQ.

http://kbase.redhat.com/faq/FAQ_43_4053.shtm — Details booting operating systems other than Linux.

http://www.linuxgazette.com/issue64/kohli.html — An introductory article discussing the configuration of GRUB on a system from scratch, including an overview of GRUB command line options.