Cakewalk
Cakewalk offers a range of professional tools for windows-based music and sound production.
http://www.cakewalk.com/
Chord Finder
Excellent resource for finding guitar chords, easy to read graphical interface. including 6ths, 9ths and other jazz chords. all chords available as midi-files.
http://chordfind.com/
Cubase
Cubase
http://www.cubase.net/
GuitarPro
Guitar pro is a multitrack tablature editor for guitar, bass and banjo. the complet tool for composers, groups or simply for guitar players.
http://www.guitar-pro.com/