While I can't claim to have thought of this, it's brought up infrequently enough that I wanted to devote a post to a quick method I use for cashing in my emblems.
If you're anything like me, you probably run a few heroic dungeons a week (if not every day) and have a surplus of Emblems of Triumph. One popular technique is to use the vendor in Dalaran to trade down for Emblems of Heroism, and then convert those into gems.
However, if you look a bit more closely at the vendors you'll notice that the Emblem of Valor vendor sells wrist armor that is bind on equip! For 60 emblems you can purchase the Bracers of Dalaran's Parapets, which is a nice-ish entry level tanking piece. While you can test the waters with the other pieces, I generally go for the tanking bracers because 1) there's always a market for tank gear, and 2) most importantly, tanks are willing to overpay more than perhaps any other spec.
This isn't a cash cow, but it is a great way to liquidate your supply of otherwise useless emblems. Check your AH, as server mileage may vary, but it's a pretty quick and dirty math exercise to determine how to proceed. Assuming you are a JC, or have access to one, if the selling price of 3 top epic gems is less than the cost of bracers, then go for the bracers. If for some reason gems go for a lot (and I can't imagine how they would at this point), then go ahead and cash in for gems. Most cut red gems on my server go for 150-ish gold on a good day, so even rounding up very liberally, let's say I could sell 3 for 600g total. I usually sell the bracers at 900g, for a 50% increase in what I could expect from cut gems. The volumes aren't super high, but I average about 3 sales a month (my scan below is missing one as well):
One additional reason I like this so much is that the deposit cost is de minimis. If it takes a week or so for these to sell, no big deal, you're not wasting nearly as much on deposit fees as you would for the gems. Plus, given that my primary professions are enchanting and jewelcrafting, it helps me avoid concentration risk.