Keepers of Time
Even though you're only able to do this rep grind through dungeons, it's worth it for the multitude of good rogue items. Honored rep gets you the third part of the Opportunist's Set, the spaulders. But the real prizes are at exalted: the excellent but unreliable Riftmaker dagger, and the PvP trinket with an added aggro drop, the Timelapse Shard. Black Morass runs can net you a ton of rep, along with the chance at some nifty items from the bosses.
One of the easier grinds, the Kurenai/Mag'har is only worth it if you really want a riding talbuk. The rest of the stuff is mostly hunter loot, with one exception: the decent pre-Kara shoulders at revered.
You can pick up the Opportunist's Leather Tunic here at revered. Pushing on to exalted gets you the Shapeshifter's Signet, which (as the name suggests) is really better for a druid. Skip it unless you're getting the Opportunist's set.
Okay, we all want to ride dragons, but that's not really rogue-specific. So we'll pass by this one for now, stopping to note that the 45 stamina on the Commander's Badge can be pretty useful.
It's the new Cenarion Circle, in that it's mind-numbing, confusing, and complicated enough that you need a road map to figure out just what you're supposed to do. That being said, it's not too difficult, and there's three rogue items: the mediocre Crystalforged Trinket (which is better for druids), the semi-decent Crystalline Crossbow (better for tanks), and the Shard-Bound Bracers (perfect for rogues, and will last a long time when socketed correctly.) You may also be able to create a Crystal-Infused Shiv or Crystalweave Cape while grinding the rep, or receive the rather nice Ring of the Overseer for beating the boss Shartuul.
Like the Netherwing, this is mostly useful if you want a mount. But you can pick up a fall-speed reducing cape at revered, and exalted brings you the Skyguard Silver Cross, which is a wonderful farming tool for rogues.
Shattered Sun Offensive
This faction will be new in patch 2.4, and is definitely worth it for new 70 rogues simply for the available weapons. Revered status can get you a decent main hand dagger, and a very nice slow-speed sword. But the real prizes are the exalted trinkets. (What is it with exalted and trinkets?) The effects depend on if you're aligned with the Aldor or the Scryers. The Shattered Sun Pendant of Might can proc and give you 200 AP (Aldor) or 100 crit rating (Scryers) for 10 seconds. The pendant of Resolve, however, is far better for Scryers (100 expertise) than Aldor (100 dodge rating.)
Don't. You have your choice of a bad dagger or a weird cape. Unless you're desperate for a tiny spore bat, just don't.
The Aldor/The Scryers
Aldor/Scryers was the big choice in BC, and while it was difficult for a lot of classes, it's pretty darn easy for rogues. Aldor is for sword rogues; Scryers is for dagger. If you're not sure what you're going to spec at 70, the rewards for Aldor alignment are the ring Lightwarden's Band and the main-hand sword Vindicator's Brand. Scryers, on the other hand, can buy some okay leggings and the off-hand dagger Retainer's Blade. All these items, however, will eventually be replaced. A better way to make your choice is to look at the shoulder inscriptions available. The Aldor get the Inscription and Greater Inscription of Vengeance, which focus mainly on attack power. The Scryers get the more crit-centric Inscription and Greater Inscription of the Blade. Choose wisely, unless you really want to make the long trek over to the other side.
In a less-than-surprising development, this band of lawless smugglers carries some good rogue items. Haramad's Bargain is better for a feral druid, and Gift of the Ethereal is merely a leveling weapon, but the Consortium Blaster and Nomad's Leggings make getting to at least revered worth it, assuming you don't already have superior pants. Guile of Khoraazi looks nice on the surface, but is a little fast for mainhand and a little slow for offhand. Definitely do Consortium if you're a jewelcrafter, though -- you can make a ton of money off the patterns you purchase there.
Dang hippie energy beings. You'll need to get revered to finish off your Opportunist's set and grab the leggings, but other than that, you can pass.
What do you think are the most important reps for rogues?