I've been a leecher for quite some time now, figured I could help some people out. Everybody knew back in WotLK that you could bid on greens and have them DE'd for mats and sell for a profit. Same applies now, just that with Cataclysm out for a while, people are starting to buy it for more expensive prices. Look in the AH for level 74-78 uncommon items (78 because some 79 and up are cata greens). These all DE for around 3-5 infinite dusts a piece, and you can bid on them for around 3-6 gold! I've been doing this for a while and made around 15k gold from it in the last 2 weeks. Just be sure to sell at the right time, as my server fluctates from 4g to 9g, and you wouldnt want to miss out on all of that money.
edit: used search for infinite dust, DE dust, low level green disenchant. found nothing from 2011, or late 2010