Place a redstone torch on top of a sticky piston facing upwards with redstone leading off to whatever you want powered. The redstone line should be lit up.
Link up the sticky piston to a button - make sure it and the powered redstone trial don't link up!
When you press the button, the redstone torch should be moved up, unpowering the redstone trail and turn off a lamp or unextend a piston or whatever.

you should be able to make a pretty rough but functional piston door with this (which is the whole reason I tried to find this out)
Happy building!