I've tried skinning a bunch of times, but I never ended up keeping it up. Its a very easy profession to level, but I never saw the benefit compared to having herbalism or mining.
Leveling my druid to 70 now though, I decided to take up leatherworking. Since the prices of skins are ridiculously high(especially for the thick leather/rugged leather/knothide leather segment, and I need SO much of it) I decided to go leatherworking/skinning and for the first time since beginning the game, take a profession just to feed another one.
Well, I got skinning up to par for northrend skinning, but I needed many more skins than what I got from simply powerleveling the profession. After reading up a bit on where to get the necessary skins, I switched my 80 pally's unused mining profession to skinning as well, and leveled it up to 300. Her other profession is enchanting.
Although I've yet to try SFK and WC for skins, I did try quite a few other spots that were fair producers.
The south end of Dustwallow Marsh was the first good producer. The mobs in that area used to be elites, but have since been changed to non-elites. However, their loot tables for skinning have not been changed. Heavy leather was dropping many times in pairs per skin, increasing the amount I picked up per/hour by quite a bit. Sunken Temple is the next one of course, once you need thick leather. However, the amount of unneeded green dragonscales that drop made me cringe a bit, since I don't use them and really can't sell them without multiple postings. After that, I headed to Dire Maul north(after getting the key from east) and started farming the little area with dogs as soon as you get in.
A clear with my prot pally(with nowhere near good gear. Sitting at 25k health unbuffed with a lot of Tier 7 pieces and blues) takes 5 minutes, 6 if I'm slow at looting. I was going to start recording how I did and decided to do it here instead so I could share with everyone else how spectacular a farming area it is.
After the first 5 clears:
171 rugged leather
13 rugged hide
33 thick leather
8 illusion dust
4 greater eternal essences
2 large brilliant shards
17G in vendor trash
Not sure what everyone else's servers look like, but rugged leather on mine sell for 30-40G per stack usually, so that's 250G+ just from those. Having enchanting as a secondary obviously helps a bit as well, since those greater eternals will sell for 50G at least. Add in the rest of the stuff, and I'm sitting at a solid 350G at least being very conservative.
For 25 minutes of work, its not bad. I'm going to do it a few more times and post up my results here for everyone to gander at, if they like.