These boards allow you to use your own 5mm LED as a LilyPad LED. If you've ever tried to 'spiral' the legs on an LED so that you can wrap conductive thread through the loop, you know why this board was created. When twisting, the legs on the LED can potentially break off. This board allows the user to solder in a through hole device and then connect easily to conductive thread, forming a much more robust and sturdy connection. These boards work great to link anything through-hole (such as resistors, transistors, wires, connectors, etc) from soldered to conductive thread. Because of the 0.1" spacing for the LED, these can also be used to connect sensors, switches, etc.
The LilyPad LED PCB is a design concepted by Felicia Williams of Boulder, Colorado.