So, the first project I started, and still haven't finished, is a pair of metal DDR pads. I actually got one to the point of testing, but it just never really felt quite right. So, one of these days I'll go back to the drawing board and do a proper redesign. In the meantime you can see what the existing version looks like at least.
Of course, to make the pad look nice, you need some nice arrows. So, here are slightly closer views of the actual arrow panels. If I can drag up the actual source files sometime I'll try to post them out here.
After finishing that pad, at least as much as it was ever finished, I decided to take a different approach for my next attempt. Rather than having a controller hanging off the pad, I'd build a proper control box. Ironically, we use it now for Para Para Paradise, which has the same primary controls (left, right, start). The cool thing you can't easily see is that there's a three position switch on top of the unit. That changes the mapping of the green button, so it can be O for PS2(JP) games, X for PS2(US) or XBox games, and Start for Stepmania.