In very early stages: http://spiderworm.github.io/spatial-ui/ (Chrome recommended)

What is it?

A starship bridge simulator, where you and a group of friends (or enemies, if you prefer) will take control of the bridge on a major starship, working together to complete combat and exploration missions in a variety of space vessels, both primitive and advanced.

When will it be ready?

We hope to have a simple mission or two ready to play by Summer 2014.  We will continue adding features and missions hopefully for years to come.

Is it moddable?

Absolutely.  Developers will be able to create mods, which are also known as "stories".  Stories are server side, and all resources for the story (including models, textures, sounds) are stored service side and delivered to the client on an JIT basis.  This allows for clients to connect to stories of all types and allows the story writer to be wildly creative.  It also allows for persistant stories, where you could have a role (security, helm, weapons, engineering, captain, whatever) on a starship for years, with new adventures being added by a Game Master in real-time.

I work on the client, and my good friend glikker is working on the server.  His code so far is at: https://github.com/glikker/starsim .  We'll be providing detailed modding information in the near future.