companions tab is starting to take shape. The tab is accessible by opening your character pane and clicking on the "pets" tab. From there, you can toggle between your companion and mount spells. Hunters and warlocks will also be able to preview their combat pets.
Note there are still some bugs, such as not being able to move beyond your first page of pets and there are some pets, like the Tiny Snowman, that aren't yet learnable. My guess is that they're still working on how to upgrade companions that require a reagent or a wearable item. But there IS hope—I noticed that my Bloodsail Admiral's Hat now includes the following text in the tooltip: "Teaches you how to summon this companion." Perhaps it will become a learnable spell that simply requires the hat to be worn when casting. Only time will tell...
P.S. And yes... those of you who looked closely at the above linked screenie can tell that I've been testing the new barbershop.
Preview: Companions Tab
August 02, 2008