Warning: This "Minecraft on LSD" mod may make you feel nauseous. It's also incredible.
Part of the appeal of indie darling Minecraft is how endlessly customizable it is thanks to its low-powered graphics and easily-moddable design. If players want, they can download all sorts of different shaders and mods to influence the appearance of the blocky game world.
It just so happens that a particular combination - mixing this shader mod with this other one - makes it seem like the Minecraft player character has just popped a tab or two of heavy-duty acid. It's really fascinating to watch how the background distorts and changes in the distance, but then flattens out when the player actually approaches it.
If you're interested in installing the mod for yourself, its creator (or, rather, its discoverer) gives the following instructions: "Copy it to a txt file then rename the txt to - base.vsh, then, making sure to backup your existing base.vsh drag it into the shaders folder located inside your minecraft.jar (once the GLSL shaders mod is installed of course)."
It's Greek to me, because I don't play Minecraft. But if you have a healthy stomach for vertigo, why not give it a try?