WowAce

Tracks rare drops, including companions and mounts

Officially the original source for where things are in the Broken Isles, in HandyNotes

The original HandyNotes source for where things are in Battle for Azeroth

The original source for where things are in Pandaria

Officially the original source of knowledge of where things are in Draenor during Warlords, in HandyNotes

Find five Ephemeral Crystals, get a pink hippogryph

Collectinator is an addon which will scan your pets and mounts and provide information on how to obtain them.

Add-on that shows which mounts can be farmed this week

mount and companion manager

Dynamic mount macro generator

Displays Pet Info for Hunters and Warlocks. Also keeps track of Stables and Pet and Demon skills.

Auto and random summon highly customizable for your pets and mounts, with Data Broker support.

The One-Key-Mount™ — Simple to use, configured with Rock

Pet Theory

Shows the health of the player's current bodyguard.

MiniPet, Always keep your little companion with you, based on the work of Carra.

A Mount and Companion manager

Add-on that shows which battle pets can be farmed this week

Don't underestimate your little critters!

Generate a macro with random mounts