The unstoppable Minecraft has a new update available, which is known as "The Horse Update". The Horse Update pushes Minecraft up to version 1.6.1, which - you guessed it - includes horses in the game now.
Mojang have also provided donkeys and mules, which can be bred and spawned naturally. These animals do require taming before you can ride them, but once you do you can ride them around in the game world, adding chests to their saddles. You can also name your horses like other 'pets' and add all sorts of armor like iron and diamond.
The Horse Update also includes improvements, such as a conversion tool that lets you convert texture packs to resource packs, which will allow you to add sounds to different items. This update includes the usual performance and stability fixes, as well as improvements in riding mounts, respiration enhancements, extra tooltips, carpets in different colors which can be added on blocks, and like you can do stain wool you can now do stained clay.
For the builder in you, there's also hardened clay which is just as hard as stone.