Probably multi-touch devices are the most exciting way to give inputs to a computer. Since having a multi-touch by buying a Microsoft Surface or an Apple iPhone would be too easy we want to make our own multi-touch device. Just for fun and to see what's the future without having to spend too much.
Surfing the web I found some interesting projects. In my opinion these are the most valuable for the reason I'm going to explain in the next paragraphs.
Probably this is the simpler multi-touch device I've seen. You can build it with extremely cheap materials and I think that it is ideal if you don't want to spend too much time in making the device. On the other side this is only a input device, you won't have your screen directly on your MTMini.
This is a very useful page: it explains what kinds of multi-touch display you can build with some technology tips and the theory behind them. Since the prototype proposed uses Infrared instead of light it's more accurate but it requires more work to make it and it's a bit more expensive. It worths reading this link just to know a little of theory that could be useful even in other projects.
This is probably the best example of DIY multi-touch application. If you ever wanted to do something like Tom Cruise in Minority Report does you have to build this device. All you need is a Wii Remote and a projector.
Before tcid and sirus begin complaining :-) because of I haven't mentioned their beloved OSX in the whole post I tell you that Bridger is working on a Multi-Touch device for OSX. Since TouchLib is Windows-Only he had to do some work to support his OS but seems he is doing a good job. Seth and BalXwan uses TouchLib, Johnny works in C# so you have to use Windows to control one of them device.