If you've been longing to gallop hard across the blocky plains and barren sands of Minecraft, now's the time to jump back in. Rideable horses have been added to the ever-expanding sandbox (based on those of the popular Mo' Creatures mod), along with horse armor, leashes, and a few other items.
Taming a wild horse will involve feeding it, and attempting to ride it like you would a saddled pig. Unlike our former porcine mounts of choice, however, horses can throw you off before they learn to recognize you as their master. Once you're partners, you can craft saddles and armor for your horse, and hitch them to items in the environment with a new leash item. Horses have variable amounts of health points, and can be selectively bred to maximize this trait—two hardy horses have a chance of producing an even hardier foal.
The update also brings some "huge changes to the base technology of the game", which now uses Java 6 and requires a minimum of OpenGL 2.0. You can read the full changes list for the update on the Minecraft Wiki .