PiP for Mac - Always on top window preview similar to the popular windows only OnTopReplica
Circuito.io - Instant code and wiring for your project
PiPer - A DIY Minecraft computer to build gadgets
library.io - Learn electronics and easily create circuit boards online
Helium - Helium lets you accept payments by credit card for anything you want to sell online.
B4R - Development tool for native Arduino programs.