Google 3D Aquarium still shocks me
WebGL and Javscript are not really new technique. They can be used for desgining cool 3D stuff. Lately, Google has made a series of demos using WebGL and also open sourced these demos.
Among these demos, Aquarium is one which can definitely impress you.
Note: in order to run WebGL, you will have to need specific build of broswer. Google Canary build of Chrome is a good one.