Shift register control of stepper motors

I sell a shift register based sixteen channel high current shield for Arduino. I've just release a library, shiftStepper, that allows you to drive as many as four unipolar stepper motors from a single shield, and up to twenty-five shields from a single Arduino (although update speed goes to hell).

It's still pretty alpha at this point, but it works and it's pretty fast -- with the latest version, a single shield and four stepper motors, the update takes ~145 microseconds.

You can read the write-up of the library at my blog and download the latest version as a zip archive.

And here's a video of it driving some stepper motors: http://video.google.com/a/ife/f28ebd1bb1cb2af9