nothing special, just a 25 pound(11.3 kilo) wooden usb dance pad based on a microsoft keyboard
YASDP
Yet
Another
Stupid
Dance
Pad

Step 1: Drawing the Pattern

First you want to visualize how the pad should be, choose the sizes of the buttons and the layout you want
alot of people will choose a basic 4 button pad
while others will add 2 extra buttons to the top right and top left for a 6 button pad
you can also add 2 more to bottom right and left and possibly even extras for enter and escape(or extra functions)

Step 2: Cutting the Pattern

In this step i drilled out a rough pattern around each button(and yes i know they arnt perfect) and then used a dremel multipro with number 561 multipurpose cutting bit(although there is ALOT of bits that'd work just as good and probably some that would work better) actually used the dremel to cut the corners of the actual board too(through 2 inches of wood)

Step 3: Cutting a Path for the Internal Wiring

used the dremel yet again, freehand cutting a quarter inch deep path using another cutting bit to make a path for the buttons, same cutting bit but pressed deeper to make an area for the microswitches

Step 4: Solder It All Up

had to scrape the black stuff that contacted the membrane off so the solder would stick but other than that, it all went smoothly, used some regular wire i had laying around, match all the pieces together

Step 5: Secure the Buttons

any piece of cloth or vinyl or even glue will work here
here, i used a old pillow case, make sure the buttons have room to move upward so the switches can reset

Step 6: Put It Together

i placed all of the buttons back into the correct places on the foam rubber, proper positions and alignment makes things easier to get together

Step 7: Finishing It Up

drilled 4 holes, 1 at each corner slightly larger than the bolts so they would slide freely into place
this pad was made for the free ddr clone, stepmania(get it from http://www.stepmania.com its playable on a keyboard as well as with a dance pad including official ddr pads through an adapter)
you can make your own step files for any song you have through the built in editor
or use step files that other users have made and distributed through the internet(only legal if you own the song on cd if the song itself is included)
dancing monkeys is available from http://monket.net/dancing-monkeys/ which automates the process of step generation but is slow and at times unreliable

a little word of advise, check your wiring before assembling!
i ended up with a fully working pad with the down and right buttons reversed!
5 minutes opening it back up and another 5 resoldering 2 wires and it was fixed

the switches are from american science and surplus(if you got 1 near you, i highly recomend checking them out www.sciplus.com even if you just get a plastic dinosaur or somthing, they rock)