SculptGL is a web sculpting application, powered by WebGL and JavaScript.
The source code can be found on github here.

Shortcuts so far :

If you want a standalone version, it's here (nodejs version, so same performance as the web version).
Also, keep in mind that I often update the web version (unlike the standalone version).

For the old SculptGL version you can play with it here.
You can visit the old branch on the the github page.