Amazing sandbox building game Minecraft is temporarily free. The developer is having scaling problems, something to do with selling 100x more copies than he ever dreamt. So until he fixes his backend he's making the game free. Try it out! And if you like it, pay the 10 eurobucks to buy it once he's gotten his problems sorted.
My most recent Minecraft project was making paintings. Paintings require cloth. There are no sheep in multiplayer yet, so the only way to make cloth is with string. String drops from spiders. So naturally, the way to make a painting in Minecraft is to find some cactus, then take it deep underground to a spider generator and get that cactus growing. Build a cage of cactus bars separating yourself from the spiders, then wait patiently for the spiders to beat themselves to death against the cactus, then collect all the string. What could be more natural?
It takes about 4 minutes to collect 9 string to make 1 cloth. 4 terrifying minutes of spider screeching. The worst is when two spiders spawn at once and one jumps on top of the other and comes lunging at you. I lost my gold hat and boots to that trick. Now the bars go all the way to the ceiling. I also improved it later by adding a little water stream that flows through the bars; now the string just floats to me.