I have been messing around with fiducial marker tracking for tangible computer interfaces for sometime now. We produced the London College of Fashion (LCF) experience using a modified dual marker system with ReacTIVision and Processing. Karsten Schmidt coded an evolutionary algorithm to grow his own version Fid.gen, and we used the augmented reality ARToolkit for a recent gesture based interactive (my flickr set) for Nokia Siemens Networks.
Japanese Flash developer ‘Saqoosha‘ made FLARToolkit which is basically a port of the Java ARToolkit into AS3, creating a way to publish to the web with ease (as long as you have the printed markers and a web cam) Check out his SWF demo (Flash 9 player), you can also get the source code, and marker pdf. If you do not have a web cam there is a desktop fireworks demo video.