NtEd - Music Score Notation editor.
Band-in-a-Box - Band-in-a-Box is so easy to use!
DaCapo Editor - 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.
KGuitar - Kguitar is a guitar tablature editor for Linux, featuring:
Sibelius - Sibelius is a virtual score creation tool which allows composers to easily create new piano scores, developed by Avid.
Pretty Captions - Create beautiful captions for Instagram and other platforms