Leatherworking

Allakhazam's Leatherworking page is here, and Thottbott's is here. Thottbot's is a little better, IMO, but if you're interested in drop- or vendor-only patterns, Allakhazam's page lists these on their page, just click the <Pattern:X> link under the name of the item on the list above to see where to get it.

For Alliance, the Artisan Leatherworker is in Darnassus, and the Maser Leatherworker is in Aerie Peak.

After level 40, and when your leatherworking skill is sufficiently high (not sure what skill lvl is required), you can specialize in one of the 3 branches of leatherworking:

Tribal Leatherworking quest Items generally boost intellect and spirit, good for druids.

Elemental Leatherworking quest Items generally boost agility and stamina, good for rogues and possibly hunters.

Dragonscale Leatherworking quest Makes mail, good for hunters possibly, since they can train to wear mail at lvl 40.