Keepers of Time (R)
In order to start grinding reputation with the Keepers of Time, you'll need to complete Caverns of Time: Durnholde, to unlock the ability to run Caverns of Time: Black Morass. At that point, you can run either repeatedly until you reach the desired reputation level.
Their designs are worth the effort. At honored, you can purchase a meta gem cut, [Design: Enigmatic Skyfire Diamond], and an awesome bind on pick-up cut for tanks, [Design: Facet of Eternity].
At revered, a bind on pick-up caster trinket becomes available, [Design: Living Ruby Serpent]. You will also be able to purchase a bind on equip fire resist plus stamina necklace that you'll be able to sell or give away. [Design: Pendant of Frozen Flame] is another necklace in the series discussed last week, and is helpful to bring for certain boss fights.
Finally, once revered, you can purchase another bind on pick-up cut that will suit melee classes and hunters quite well, as [Design: Stone of Blades] offers a decent amount of critical strike rating.
Scale of the Sands (R)
This faction is another raiding faction, this time associated with Mount Hyjal, and related in lore to the Keepers of Time. The jewelcrafting rewards are the same as can be acquired from the Shattered Sun Offensive, although they don't nearly offer as many designs.
The reasoning behind this is that the purple gems such as [Lionseye] drop in this dungeon, as well as from the Sunwell Plateau.
Cenarion Expedition (E)
The rewards from this faction might not be your cup of tea. The first design, [Design: Nightseye Panther], acquired at revered, is another bind on pick-up trinket that only you can use. While it is useful for rogues and kitty druids, jewelcrafters of other classes won't be making them. Even though it adds attack power, there are other trinkets out there that offer better itemization for non-stealthing classes that benefit from AP.
At exalted, you'll acquire a new ring design, [Design: The Natural Ward]. Providing stamina and nature resistance, its main use is for boss fights requiring extra resistance. Still, it is bind on equip, so you might find buyers.
The Consortium is the faction with which to grind reputation for any jewelcrafter, along with the Shattered Sun Offensive as of patch 2.4. Not only do these tradesmen offer several designs, but they also award bags of gems each month, and the quality of the contents depends partly on your level of reputation.
A monthly bag of free materials, often including blue quality gems if you are revered or exalted, is nothing to sneeze at.
At friendly, you can purchase two new designs, both of which are great for leveling your skill. [Design: Luminous Flame Spessarite] and [Design: Shifting Shadow Draenite] might also net you a little money on the side.
Honored reputation brings five new designs, including two meta gem cuts. [Design: Delicate Blood Garnet], [Design: Lustrous Azure Moonstone] and [Design: Thick Golden Draenite] are all green quality cuts, generally selling on the auction house for roughly one to ten gold, depending on server, supply and demand.
[Design: Powerful Earthstorm Diamond] is a keen meta gem for tanks, warlocks, or anyone else stacking stamina. [Design: Swift Skyfire Diamond] is nice for classes that benefit from attack power, and the speed boost is a nice addition, although many players will use the boot enchant.
At revered, another four designs open up. [Design: Pendant of the Null Rune] is another pendant in the stamina and resist series, and this one offers protection from arcane spells.
[Design: Bracing Earthstorm Diamond] is an awesome healing meta, especially for non-paladins, whose built-in threat reduction isn't as strong. [Design: Crimson Sun] is another bind on pick-up gem, so jewelcrafters looking for attack power will want this cut.
Not to be forgotten, spellcasters will also get a bind on pick-up gem cut at revered, [Design: Don Julio's Heart], offering a fair amount of spell damage.
At exalted, another meta cut becomes purchasable, [Design: Relentless Earthstorm Diamond]. With the +agility and +critical strike damage, this is great for rogues, feral druids, dps warriors, enhancement shamans, and hunters, especially survival.
Shattered Sun Offensive (E)
This faction offers a whopping number of recipes to its jewelcrafting allies, although there are two catches. First of all, you'll need to be level 70 in order to start grinding reputation with the faction. Secondly, most of the cuts require gems that drop in the high-end raiding instance, Sunwell Plateau, although they can also be purchased from a vendor at Sun's Reach Harbor for 15 badges a piece.
While you can purchase them from the auction house, you'll need a fat wallet and the ability to float a large sum of investment (300-400 gold on my server) in that gem until you make the sale. For convenience, I will arrange the patterns by the gems they use, and code them with (F), (H), and (R) or (E) where appropriate.
[Design: Bold Crimson Spinel] (F)
[Design: Bright Crimson Spinel] (F)
[Design: Delicate Crimson Spinel] (F)
[Design: Runed Crimson Spinel] (F)
[Design: Subtle Crimson Spinel] (F)
[Design: Teardrop Crimson Spinel] (F)
[Design: Figurine - Crimson Serpent] (R)
[Design: Flashing Crimson Spinel] (E)
[Design: Glinting Pyrestone] (H)
[Design: Luminous Pyrestone] (H)
[Design: Potent Pyrestone] (H)
[Design: Wicked Pyrestone] (R)
[Design: Figurine - Khorium Boar] (R)
[Design: Reckless Pyrestone] (R)
[Design: Veiled Pyrestone] (E)
[Design: Inscribed Pyrestone] (E)
[Design: Brilliant Lionseye] (F)
[Design: Gleaming Lionseye] (F)
[Design: Smooth Lionseye] (F)
[Design: Thick Lionseye] (F)
[Design: Quick Lionseye] (R)
[Design: Rigid Lionseye] (R)
[Design: Great Lionseye] (E)
[Design: Mystic Lionseye] (E)
[Design: Lustrous Empyrean Sapphire] (F)
[Design: Solid Empyrean Sapphire] (F)
[Design: Sparkling Empyrean Sapphire] (F)
[Design: Figurine - Empyrean Tortoise] (R)
[Design: Stormy Empyrean Sapphire] (E)
[Design: Dazzling Seaspray Emerald] (H)
[Design: Radiant Seaspray Emerald] (H)
[Design: Jagged Seaspray Emerald] (H)
[Design: Figurine - Seaspray Albatross] (R)
[Design: Enduring Seaspray Emerald] (R)
[Design: Steady Seaspray Emerald] (R)
[Design: Forceful Seaspray Emerald] (R)
[Design: Balanced Shadowsong Amethyst] (H)
[Design: Infused Shadowsong Amethyst] (H)
[Design: Glowing Shadowsong Amethyst] (H)
[Design: Royal Shadowsong Amethyst] (R)
[Design: Figurine - Shadowsong Panther] (R)
[Design: Purified Shadowsong Amethyst] (E)
[Design: Shifting Shadowsong Amethyst] (E)
[Design: Sovereign Shadowsong Amethyst] (E)
[Design: Ember Skyfire Diamond] (R)
[Design: Eternal Earthstorm Diamond] (R)
[Design: Regal Nightseye] (R)
[Design: Forceful Talasite] (E)
[Design: Quick Dawnstone] (E)
[Design: Reckless Noble Topaz] (E)
Many of the above designs are quite profitable, and often requested by raiders needing to gem a new item. Although the trinkets are not bind on equip, there is a fair amount of variety, which is helpful if you're a hybrid. Unless you collect recipes, you can save some gold by only purchasing the trinket designs that you plan to use.