I -think- middle C is the (under standard tuning) 8th fret on the 6th string.

Have a look at the following ways of representing musical instrument ranges.

Some graphical ways of looking at musical ranges:
http://members.aol.com/pjay99site/Instrumentranges.htm
http://en.wikipedia.org/wiki/Range_(music)

Musical Instrument Ranges as they appear on the musical staff:
http://www.dolmetsch.com/musictheory29.htm

This should really be in the Music Theory section.. :)