As most pet collectors know there is only one source of reliable pet information and thats at warcraftpets.com, Breanni keeps the site up to date for all avid pet collectors. I myself was an avid collector amassing 111 pets until I stopped near the end of wrath.
Mageshadow posted on new drop zones for the new whelps before Cataclysm was released but I cant seem to find the post anywhere.
Im going to concentrate on the 4 whelps that drop from various zones around Azeroth:
This one is a zone drop in the Wetlands, it used to drop off the Whelps around Mudsprocket before Deathwing changed the loot tables...... Wetlands is a 25-30 zone and again a 1 in 1000 drop rate.
Farming for this used to be in the little corner of the Badlands well known for Mithril to us old school farmers. You can now find it in drops from Ebon Whelps in the Wetlands, Nyxondra's Broodling in the Badlands and also Flamescale Broodling in Burning Steppes. All different level zones but more importantly these little guys only drop from specific NPC's. 1 in 1000 drop rate.
My favourite Whelp pet. I used to love farming this little beggar. I most certainly wasted a few hours of my life farming this. The old drop place was in the Swamp of Sorrows but now the reside in Northern Feralas and the are lootable from Noxious Whelps Feralas is a 35 - 40 zone.
The reason I have selected these 4 pets is double edged. On one side is obviously the gold making aspect of it but I love farming these when I have a low level alt that needs a boost up. These are great XP if you have rested bonus and now even more so with guild perks.
Always use an alt that will gain XP, ie one around the level of the mobs you need to kill. I know its obvious but farming these on your main maybe quicker but a darn sight less rewarding. Killing two birds with one stone so to speak.
I had a nice farming route set out before Deathwing came and buggered everything up for me. Wetlands, Swamp of Sorrows then Badlands. The farming just about took me through all levels to be able to kill the required mobs.
These pets sell for roughly 4k on servers and depending on the Whelp sometimes more. Specific mob pets should fetch a little more at the Auction House. Add into that the greenies which can be DE'd for materials to sell its quite a decent gold maker if your luck is in.
Nowadays the gold earned per hour is very low due to the droprate and could likely be earned elsewhere a lot quicker. It could be that you get a whelp on your first kill but more likely it will be at least 500 or 600 kills if not more.
If you are bored of farming ore, herbs, fish, trade materials, the auction house or whatever else it is you spend your time doing and want a change and a bit of XP mob killing with a goal then these little fellas are perfect to farm. Forget Archaeology as its boring as whale dump and farm these guys for some snooky pets.
One word of warning though. You will want to keep every pet you farm, thats the pet collector in you. If one drops ALWAYS kill a few more as most of these pets for some reason or wild rng drop in twos and then you have one for yourself, unless the goblin in you takes ove that is.