I'm sitting at the eve of 79, with just 2 bars to go. Hitting 79 tonight will be easy, but 80 is probably tomorrow at best. There are a few 80s in guild already but not enough to farm heroics, so I'm working to get there. By the time I do hit 80 we will have enough to do heroics until we start farming Naxx. I'm not sure when to start on Naxx though, if I should wait until we comprise a majority of the run (say about 8 slots or so) or if I should allow my officers time to level (they are sitting at 73 at the moment.) Tough decisions, no?
Anyway, I've spent the past few bars grinding on mobs in Sholazar Basin for skins to make my Eviscerator's set and I thought now would be a good time to share how I leveled/plan to level my leatherworking from 375:
375-390: Frostscale Shoulders, Iceborne Boots, or Nerubian Belt. All of these are 10 leather. Just make whatever sells best. If you're selling to the vendor, then make the shoulders.
390-395: Any of Frostscale Boots, Frostscale Gloves, Iceborne Shoulderpads, Nerubian Boots, Nerubian Shoulders. The highest vending item is the Nerubian Shoulders.
395-400: Any of Arctic Wristguards, Frostscale Bracers, Iceborne Wristguards, Nerubian Bracers. Highest vendor value is the Frostscale Bracers
At this point you can now make Fur Linings. These are great as one Arctic Fur (~40 gold on my server) is one point of Leatherworking until 425. Also, at this point, all orange recipes require Heavy Borean Leather or something more exotic.
400-405: Nerubian Leg Armor. This sells nicely on the Auction House. You could also try to Emboss your legs for points using the Reinforcements instead. In fact, I would do it anyway, since the mats are easy to come by (especially if you've run any Dragonblight instances) and the result is an epic level enchant.
405-410: At this point I would recommend making your Dark pieces, as they are likely upgrades if you meet the requirements and can actually use leatherworking gear. Personally, I made my Dark Arctic Chestpiece and 2 sets of Dark Arctic Leggings, one for DPS and one for tanking. Make a couple more to sell (Dark Frostscale Leggings, Dark Iceborne Leggings, Dark Nerubian Leggings are the cheapest to make) and you should be set.
410-415: The only guaranteed points here are Fur Linings. Buying the Fur and reenchanting your bracers may be the most economical way to level at this point.
415-420: Pack of Endless Pockets. If you are revered with Kalu'ak, make yourself a Trapper's Traveling Pack.
420-425: At this point you should be able to learn some of the recipes sold by the Fur & Leather Trader in Dalaran. Learn the ones appropriate to your class and spec, make them, and emboss the bracers you just made. For example, I made the Eviscerator's Bindings, Facemask, and Chestguard (the shoulders weren't enough of an upgrade.) I then embossed the Bindings with +90 Stamina, as I use them for tanking. These items are pretty well sought after, so if you don't get any benefit, I would recommend buying one pattern and selling 5 of it. The Wristguards are the cheapset to make.
425 and further: At this point I would finish out the rest of your set, or make the epic leg armor kits. Again, chitin is pretty easy to come by, and Arctic Furs are common enough as to be fairly inexpensive on the AH. I would recommend making Frosthide Leg Armors and selling them. When you hit 440, you can learn any recipe currently in the game, so I wouldn't worry too much about hitting 450.
I had a guildie place an order for an entire set of Eviscerator's yesterday, which I'm happy to report got my Leatherworking to 433. Now I just need to finish my set (or at least the ones that are upgrades) and then start selling those armor kits!
The only bad thing is that all the fur you're using for crafting the kits can also be bought for more recipes.
That's all for now.