ARToolKit has been around for a while, enabling professionals and amateurs around the world to composite properly scaled and oriented 3d models on top of real world video feeds through glyph tracking.  A few years back it was mostly found in the hands of interactive artists and new media guys, searching for problems that can be solved with this particular augmented reality solution.  Nowadays, you might see it in relatively mainstream commercial stuff like this Mini Cabrio ad.

In Japan, they've already done the obvious (see: Dennou Figure ARis), but I personally find the effects done by this z8halt76 dude far more interesting.  Basically, he's using ARToolKit to pull off some of the cool visual effects one sees when magic is performed in the anime series Magical Girl Lyrical Nanoha.  Things like obscenely huge magic hammers and stuff are done easily by putting some glyphs on a cube on the end of a rod.  Even cooler things happen when he decides to put a glyph on himself...