Simple design for castle gate (portcullis) using redstone wiring and pistons. This design does't require gravity blocks (sand/gravel).
Update (2012-02-11): I remade this gate to let you better undestand how to hide wire underground, it's in 1.1 :)
DL: http://www.mediafire.com/?v9kskdzfvml9mav enjoy :)
Update (2012-04-24): NOTE: Block placement in this video are very important, place blocks like I did in order for piston not to extend before wiring :)