wxWidgets - wxWidgets: Cross-Platform GUI Library
Pygame - Pygame is a set of Python modules designed for writing games.
Electron - Build cross platform desktop apps with web technologies
SDL - Simple DirectMedia Layer is a cross-platform multimedia library designed to provide low level...
GTK - GTK+ is a multi-platform toolkit for creating graphical user interfaces.
Penny - Penny is a personal finance app that takes the pain out of keeping track of your finances.