Quite a few people wanted some clarification on the Championing system mentioned in previous editions of Ask a Beta Tester, so I'll try to do just that: The Championing system is not retroactive, and by that I mean old factions are not included in it. You can't use this to grind Orgrimmar or Honor Hold or whatever in level 80 dungeons. It only applies to Wrath reputations, and so far, not even all of those.
It only counts towards the 'big four' of Northrend as far as I can see. Those reputations are: The Kirin Tor, The Argent Crusade, The Knights of the Ebon Blade, and the Wyrmrest Accord. You should be able to get really, really high reputation with the Valiance Expedition/Warsong Offensive just through questing, but I wouldn't be surprised if we saw a Tabard for them soon, too. The little people like the Kalu'ak are, so far, not included in this system.
Read on for more answers to your questions!