Frozen Orbs have been sort of a weird little problem since Patch 3.3 came out. Since they automatically drop off every heroic end boss, the dungeon finder has pretty much guaranteed that there's thousands of them created every single day. However, the Emblems of Triumph that come out of those same dungeons pretty much make most of the profession gear made with Frozen Orbs obsolete.

As a result, many of us have at least a couple stacks rotting in our banks or backpacks, and I know I personally have started outright passing on them, having nothing better to do with them. Now I sort of wish I hadn't, if only because they're finally useful as currency in Patch 3.3.3.
On the PTR, a gnome called Frozo the Renowned will trade other tradeskill items to you in exchange for the orb. The list of his wares is as follows:

• Various Eternals will cost you 1 Frozen Orb each.
• Runed Orbs cost 4 Frozen Orbs each.
• Crusader Orbs cost 6 Frozen Orbs each.
• Frozo is also currently selling Frost Lotus for 3 gold 20 silver apiece, although I'd wager that's a bug that will be fixed soon to show a Frozen Orb cost of some sort.

In short, the next time you're heroic dungeon running, you might actually want to look forward to that Frozen Orb drop again. It may just be useful come patch time.

Gallery: Patch 3.3.3 - User Interface Updates and Other Changes