Ken's recommended websites to learn more about guitar tunings
http://www.bigcitystring.com/tunings.htm
http://www.guitartips.addr.com/guitar_tuning_tips.html
http://www.consult-eco.ndirect.co.uk/guitar/tunings.htm
http://www.guitarsite.com/tuning.htm
http://guitar.about.com/library/weekly/aa082201a.htm
http://eceserv0.ece.wisc.edu/~sethares/alternatetunings/alternatetunings.html
http://www.win.net/mainstring/tunings.html
http://en.wikipedia.org/wiki/Guitar_tuning