Sons of Hodir items. You'll want to pick up the Greater Inscription of the Axe for 40 AP and 15 Crit to shoulders. Other items are meh, though.
Argent Crusade items. They have some survival head enchants and decent items to help you break into heroics, as a DpS or Tank.
Wyrmrest Accord items. If you want to get an off-tanking set, you can get 2-3 items from this vendor, too. Their DpS stuff is... okay. Quickly replaced, but the ease of getting it makes it worth it.
Kirin Tor items. Max this one last. Basically everything they have is caster oriented. They do have a different head enchant with resist and stamina, though.
Knights of the Ebon Blade items. Great head enchant (50 AP and 20 crit) and a nice boot for DpS.
All have gem recipes if you are a JC.
I would prioritize them like this:
KotEB
SoH (only one you can't champion).
AC
WA
Kirin Tor
You'll be able to start the Wyrmrest Accord Dailies as soon as you enter NR, basically. Start in Borean Tundra and do the Coldarra chain, which opens up one daily. Then, go to Dragonblight and do the dailies in the tower, and that'll open up another. Depending on how fast you go, you can have it near exalted by 80 doing these two and the other quests.
KotEB takes a while to get to. Because I've been limited on time (and, they have some of the worst tanking stuff), I haven't even done the NR quest chain to UNLOCK this, let alone worked on it. However, it is awesome for DpS. Champion it as soon as you can, and prioritize these dailies. I don't know the minimum level for it, but it is in ICG.
SoH can't be championed, but you will want their shoulder enchants. They have a LOT of dailies, so you don't need to worry. Just start them at 77 and you should be exalted before 80. Plus, if you are willing to drop some gold, you can buy Relics of Ulduar off of the AH and turn them in for Rep.
Argent Crusade can be started earlier than the KotEB, but has worse rewards for DpS (I need to get mine up for a head enchant that'll make me raid uncirttable though, lol). Doing the tourny will give you rep with this, so it is one of the easiest to get (as most people do that for its novelty rewards anyway). And you can pay 10G a day for 100 more.
Kirin Tor is leveled up only through Championing and the profession dailies. Since it doesn't have any relevant rewards, just champion this for the achievement when you finish the rest.
Have fun.^^