[McFattyXXXL]

Necroing with what to the best of my knowledge is new information.

Per the wiki, there will also be donkeys, which reportedly will be able to carry chests on their saddles. It states that no inventory is currently available for them, but perhaps in a future update packs of donkeys can be used to shuttle large inventories between distant locations?

Yeah seems there are also zombie horses and skeleton horses to be added as well.
http://www.minecraftwiki.net/wiki/Horse

[McFattyXXXL]

ATTENTION! CRAFT THEM BEFORE 1.6
Saddles will now no longer be crafted and must be sought after in dungeons.
knowing minerealm. I say most dungeons have been looted and pillaged upon discovery.
Also added blocks of coal and certain items can also power redstone.

(Unable to put the vid into my post for some odd reason so here is the link.)

[Grelman]

ATTENTION! CRAFT THEM BEFORE 1.6
Saddles will now no longer be crafted and must be sought after in dungeons.

This along with the fact that horse armor is also exclusive to newly generated dungeons. One thing at a time I suppose, right now if only we could get some nether quartz.