Dealer Rashaad : Exotic Creatures - Worth the trip

If you happen to be leveling out in Outland, make a trip to Stormspire in Netherstorm and visit  Dealer Rashaad

This guy has a great selection of pets, see list below. And since most people tend to be lazy. These are great pets to flip back out in the AH for a tidy profit. All the pets range in cost from 40s to 40g (pre-discounts) and can easily be sold from 10g to as much as 300g.
   
Blue Dragonhawk Hatchling
Brown Rabbit Crate
Cat Carrier (Siamese)
Cockroach
Crimson Snake
Mana Wyrmling
Parrot Cage (Senegal)
Red Moth Egg

while there also take a look at some of the other vendors and buy up some of the BOE recipies that also sell really well

Breanni : Finding homes for the lost pets of Dalaran

With the new pet achievements coming out, dont forget to visit Breanni in the Dalaran pet shop, he sell 3 pets Albino Snake, Obsidian Hatchling and Calico Cat . With proper discounts you can attain these pets for ~35g (50g if you have not discounts). These can then easily be flipped for upwards of 100g +. I've sold some as high as 500g.

Engineering Cata Pet

Now with even more pet achievements, don't forget about the Engineering Pets. Especially , Personal World Destroyer.

On my server, one Personal World Destroyer, worth 1200g 0s, is made by Engineering using the following components, which cost 490g 45s 24c:

Qty	Component	Each	Total
8	[Electrified Ether]	51g 54s 12c	412g 32s 96c
8	[Handful of Obsidium Bolts]	4g 83s 86c	38g 70s 88c
10	[Obsidium Bar]	3g 94s 14c	39g 41s 40c

Even less if you craft the bolts and bars from ore, and the ether from Volatile Air.

My current cost is just under 200g. And I just sold one this week from 1200. Not bad for a profit margin.