There aren't many mounts available from WoW's annual holidays, but they're a pretty interesting example of how Blizzard's changed content through the years in an attempt to make things -- words fail me -- less annoying.
Three of WoW's annual holidays will cough up rides, and your chances of getting them -- with the benefit of the "goody bag" system implemented in patch 3.3.3 -- are much better than they used to be. Long-time players will remember the hell of farming holiday bosses with a bevy of guild alts in order to maximize the number of boss kills per day for all the mains who wanted special drops. Sometimes you got lucky. Sometimes you were everyone else.