These are invaluable resources for musicians and music arrangers.
At the listed web sites you can find a variety of Music Software Programs designed for general or special music production.
Wiki - MIDI editors and sequencers
Jazz++ MIDI and Audio Sequencer
5 Garageband alternatives for Windows
Wikipedia List of scorewriters
LilyPond Note Printing Software
MidiIllustrator music notation
Mozart Music Notation Software
MuseScore - Composition & Notation
Noteflight - Online Music Notation
Musette Free Music/Song Editor
musink - Beautiful sheet music
MobileSheets - for Windows too!