MuseScore is a free music notation and composition software available for Windows, Mac, and Linux.
Sibelius is a scorewriter program, created by Sibelius Software (now part of Avid Technology) for Microsoft Windows, OS X, and historically RISC OS.
DaCapo Editor is a free Open Source music sheet editor which allows to easily create nice looking partitions. It is available as a web application as well as a desktop application for Windows, MacOS and Linux.
Bring musical inspirations to life with the blazingly fast and intuitive Notion™ 6 music composition and performance environment. Compose when and how you want and even enter music with your own handwriting.This app doesn't have any features at the moment.
A new app for music education. Instrument Bible is a virtual fingering chart for brass, woodwind, and string instruments.