J3D
J3D was a WebGL based 3D engine. I used it for my personal experiments and demos. It's a playground rather than a production environment. It consists of a Javascript rendering engine and a C#/Unity3d scene exporter.
Most of the demos should work in all WebGL enabled browsers, including Chrome, Firefox, Opera 12 Alpha and Safari (with WebGL enabled) on desktop. Some demos only run in alpha/nightly builds of selected browsers. Some demos run in Firefox on Android.
UPDATE 2022: I reviewed the demos & experiments and updated them when necessary. WebGL is widely suported in 2022, so the experiments should work in any browser, including mobile. I also created an archive web page with all the experiments.
J3D was created by Bartek Drozdz.