I just released Noctua Sky, a new project I am working on.
This is an online planetarium (or sky map) software similar to the open source project Stellarium made by my brother.
The goal of the project is ultimately to provide a set of tools and API for amateur astronomers to share their observations online. The first step toward this is to create a JavaScript planetarium that can run directly on the browser.
Technically the application was written in C, and then compiled to JavaScript using Emscripten. I already wrote about Emscripten in an other post regarding a video game I made before.
The code is not open yet, but if you are interested in using the JavaScript client in your own website please contact me.