Interactive way to learn the Stellar API. The source is available here.
Interactive tool to test compliance protocol deployment.
Reference applications and sample code
Current status of the live and test networks. The source is available here.
SMS Client (Demo)
This is a demo of Stellar SMS Client. It was originally developed during Stellar Hack Day.
Tools and Applications created by the community
A list is maintained on Galactic Talk. Scroll down for tools that are useful for developers.