Arduino IDE - Arduino is an open-source electronics prototyping platform based on flexible, easy-to-use hardware...
VoltSim - VoltSim is an interactive realtime circuit simulator. It has digital and analog components and even Integrated Circuits. It is the perfect companion to students, hobbyists, and engineers.
PlatformIO - Next-generation IDE for IoT
Diode - diode - Android app to interact with reddit.
B4R - Development tool for native Arduino programs.
Circuit Stickers - Peel-and-stick electronics for crafting circuits.