Wolf

Wolves are new mobs set to appear in Beta 1.4, which will be released on April 1st 2011. Notch has confirmed the addition of these animals upon having breakfast with Peter Molyneux. On March 18th, 2011, a video was posted showing a preview of wolves, which are being made by Jeb. Wolves will spawn in forest and taiga biomes. Wolves may also be considered the "pet dogs" as previously mentioned by Notch. Wild wolves are usually neutral. As of now, they are not known to drop anything, nor is it known how much health they have. At the moment you can also have as many wolves as you want until Mojang comes up with a way to limit the amount you can have tamed.

Taming
They are said to be rather rare, but they will not despawn once tamed. To tame a wolf, you have to give it bones until a puff of heart particles appears and it gains a red collar, which indicates that the wolf has been tamed. The number of bones required is random. You can tame more than one wolf.

Once given enough bones, they will become friendly. They will now protect you, follow you around, and will attack mobs that you have attacked in melee. Tamed wolves will not attack mobs that you hit with arrows, nor will they attack creepers. In their current developmental state, mobs will not attack your wolves (Subject to change). A wolf's tail will rise and lower depending on its health, and it can be restored with raw pork (and possibly other foods).

Trivia

 * Wolves are the first friendly mob in Minecraft.
 * Tamed wolves will have a small red band around their neck, resembling a collar and a friendlier facial expression.
 * Wolves will turn their head to the side and beg if the player is holding a raw pork or a bone. This may happen with other kinds of food.
 * When you right-click on them they will sit and stay put.
 * Wolves can swim, and will shake water droplets off of their bodies when exiting water.
 * Jeb has said that wolves may have color variations, but he "would have to run that through notch =)".
 * When a wolf is tamed, their eyes will change from 1 white pixel and one black pixel to 2 white pixels and 1 black pixel. This change is meant to highlight a wolf's aggression when untamed.
 * Jeb has said that wolves are set to release in Beta 1.4