Macarons - Macarons is your virtual watercooler for casual conversations with colleagues you rarely meet on the hallway.
Dia - Dia is a GTK+ based diagram creation program for GNU/Linux, MacOS X, Unix, and Windows, and is released under the GPL license.
CommitTasks - A small CLI tool that combines git commit and todo list 🛠📝
draw.io - Online diagramming application
Taskbook - Like Trello but for the Terminal
yEd - yEd is a free desktop application to quickly create, import, edit, and automatically arrange diagrams. It runs on Windows, Mac OS X, and Unix/Linux.