Thunkable - Powerful but easy to use, drag-and-drop mobile app builder.
Dark Language - Holistic language, editor, and infra for building backends
MIT App Inventor - App Inventor is a cloud-based tool, which means you can create apps for phones or tablets right in your web browser.
Zukitwo - Zukitwo is a Gnome Shell and GTK theme that currently works on Gnome Shell 3.14 and the latest version of GTK.
Bubble.io - Building tech is slow and expensive. Bubble is the most powerful no-code platform for creating digital products.
Materia - Materia is a development environment to build advanced mobile and web applications.