Zookeeper 

Quick note: I'm basically idle on this add-on (as I'm sure anyone that uses it can tell) since Pandaria launched, due to Blizzard wrecking the pet summoning behavior (it's back on the GCD and it's a full re-summon vs the pet just reappearing, which breaks stealth and interrupts actions), which I'm a little annoyed about. There's a few Zookeeper data bugs of note for mounts as well -- the data incorrectly flags the Sandstone Drake as requiring 525 alchemy, and makes the Red Qiraji Battle Tank entirely unsummonable. I don't know if/when I'll be updating this, but if I do those bugs will be fixed.

A pet and mount addon. Makes handling those big piles of mounts and minipets really easy, and adds some smarts to the process as well!

A short look into its features:

• /mount command lets you pick mounts by tags randomly, specify certain ones to use or exclude, and even is smart enough to handle Northrend's quirks on where you are allowed to actually use a flying mount properly.
• /minipet command lets you pick minipets just like /mount does for mounts, with an added feature -- your last-used command is remembered, so that if you ever find yourself alone Zookeeper will bring out another pet to keep you company automatically.
• /disembark command -- it's like /dismount, but better, because it also works for vehicles!
• Enhanced companion UI shows source, tags, cost of mounts and pets, and includes a database of known companions. You can even show the ones you don't have yet.
• Tag database letting you control what type of mounts or pets you summon. Only want red horses? /mount red horse will do it. For more information, see the in-game help. Mount and pet tags are viewable in their tooltips in the companion UI in game.
• Smart mount summoning based on location and skill -- just use the smart keyword with the /mount command (/mount smart)
• Long minipet and mount macros, for more complex conditions!
• Options and in-game documentation can be found in the Blizzard Addons options section, or accessed by using the /zoo or /zookeeper commands.
• New macro conditionals for use with /mount, /minipet, /disembark for added control over what you summon based on where you are -- if you want to summon a netherdrake mount only in the Outland, for example, just use the [outland] conditional. For more information, see the in-game help.
• Zookeeper lets you mark mounts and pets as "favorites", or "forbid" certain ones from ever showing up as a random choice.
• Support for druid shapeshifting and shaman Ghost Wolf forms. They all have the tag "shapeshift" to aid in their use, plus Zookeeper will attempt to use them while moving if appropriate (Ghost Wolf only if talented to be instant). However, because these are spells and not mounts, Zookeeper can't do all the work for you. You'll need to use the /click ZookeeperSpell command after your /mount command. And because cancelling buffs is now protected, you'll have to add a /cancelform command to have your macro take you back out of form as well. As an example:
  Code:

  /cast [combat] Travel Form
  /mount [nocombat,nomounted,noform:5] smart
  /click [noform] ZookeeperSpell
  /disembark [mounted]
  /cancelform

  would be a basic druid macro that includes druid forms in its random selection and handles Travel Form in combat cleanly. I've also added a [moving] macro conditional for people that want more control over what gets used when. A similar macro for Ghost Wolf would be easy enough to do (but Ghost Wolf will only be picked while moving if it's talented to be instant, of course).