Ohai, I come back to the dc forums and I'm greeted by a minecraft thread.
I've built an automated cacti farm, a house with 5 layers of cobblestone protecting my chests from creeper attacks, an underwater house, a farm, a platform where I store most of my things, a minecart system controlled by redstone, a boat elevator and a glass path in the sky that links my house to a distant island (or continent, I'm not sure). According to Cartographer (a mapping program) I've used ~500 redstone and ~1000 torches.
Also, for those of you who want to try a very primitive alpha (there's no crafting, the mobs are different, no day/night cycle): http://minecraft.net/survivaltest
Premade survivaltest level: http://minecraft.net/survivaltest/index.jsp?user=Sniper&id=1