Some of these links have been posted before, but I wanted to show Jeef (Phillip Thomsen) how I built what he saw in the tour today. Well the most interesting things anyway.
First, the latest knowledge on Minecraft Hydraulics (Water)
Mobspawning room/pads:
Mob-elevator (Mobavator v2.0; how to get them up to the surface from the pads):
Simple mob killer (this is lava, but mine is a drowner to avoid item destruction):
In short, this guy is a genious in Minecraft-tech. Make sure you have his Youtube channel in your favourites. On top of it he knows how to make fun with creepers (
General Spazz (20 minutes in) 
)
Mushroom farm by hypnotizd:
part 1:
part 2:
part 3:
part 4:
part 5:
(tutorial)
part 6:
(improvements)