Your mileage may wary, and I have a number of things in my favor (having an epic flyer and being a Karazhan-level-geared feral druid). But I thought I'd toss out some ideas you guys might not have done yet.
1. Disenchanting items off the AH using enchantrix and/or common sense. I only list this because I know Mike will come in and say this is the best way. Also, to cover all my bases, fishing too.
2. Trees in Skettis. As an herbalist, Skettis is awesome. While doing my daily's, I do a complete round of the area, looking for the four Talonsworn Protectors (giant Ancient enemies). They are 71-72 elites, and thus easy to take down. When you herbalize them, they drop 3-5 motes of life, and 2-10 herbs (the only time I got 2 was when I got 2 black lotuses; the 10 was all felweed). Killing all 4, assuming a normal distribution and my server's market, nets you around 30-40 gold in herbs. Takes around 15 minutes if no one is farming them. However, they are usually farmed, and people can ninja-herbalize them, so be careful.
3. Running Stratholme. This is probably just for druids, and maybe for rogues. Stealthing through Stratholme, starting at the normal entrance and ending at the back entrance, allows you to take out 3 enemies. The run itself takes less than 10 minutes (I average around 7 or 8), and will get you three large brilliant shards. Then run back and do it again. The drawback is that it can only be done 5 times an hour; so that's 15 shards per hour. If you go further into UD, and kill the three ziggurat bosses on your last run, that's three more shards, though; and by then, 10 more minutes have passed so you can probably start it all over again. This method, by my server's conditions, nets me around 150-200 gold per hour, including runecloth drops, random trash, and dust/essences from random greens. Problems: you probably need stealth to do this quickly, and you need to learn how mobs in Stratholme move (all ghouls have True Sight), and occassionally an Eye of Naxxramas will call an entire group on you, which shouldn't be a death sentence, but will mess up your timing, and leave you with nasty diseases.
4. Halaa disenchanting. Every time the Alliance (or Horde, depending on side) control Halaa, check in with the vendor there. He sells, as a limited quantity, throwing stars for around 2 gold. These can be disenchanted, and usually yield 1-2 Greather Planar Essences. These essences go for 7-8 gold each on my server, so for 1 minute of work, you could potentially make over 15 gold. Worth checking it out; he gets resupplied every hour or so, it seems.
That's all for now, hope this helps some people out there. Have fun, and happy hunting. Or disenchanting and fishing.