Factions and QuartermastersHere is a list of all the (Alliance-accessible) factions with quartermasters (that is, vendors who will sell you special stuff depending on your reputation with that faction) and where those quartermasters are located.
Classic WoWArgent Dawn - Argent Quartermaster Lightspark (Chillwind Camp, Western Plaguelands)
Quartermaster Miranda Breechlock (Light's Hope Chapel, Eastern Plaguelands)
Cenarion Circle - various vendors at Cenarion Hold, Silithus
Thorium Brotherhood - Lokhtos Darkbargainer (Grim Guzzler bar, Blackrock Depths)
Timbermaw Hold - Meilosh (Timbermaw Hold, between Felwood and Winterspring)
Zandalar Tribe - Rin'wosho the Trader (Yojamba Isle, Stranglethorn Vale)
The Burning CrusadeDungeon relatedCenarion Expedition - Fedryen Swiftspear (Cenarion Refuge, Zangarmarsh)
Consortium - Karaaz (Stormspire, Netherstorm)
Paulsta'ats (Aeris Landing, Nagrand)
Ythyar (outside the Chess event, Karazhan)
Honor Hold - Logistics Officer Ulrike (Honor Hold, Hellfire Peninsula)
Keepers of Time - Alurmi (Caverns of Time, Tanaris)
Lower City - Nakodu (Lower City, Shattrath)
Sha'tar - Almaador (Terrace of Light, Shattrath)
Shattered Sun Offensive - Eldara Dawnrunner (Shattered Sun Staging Area, Isle of Quel'Danas)
Raid relatedAshtongue Deathsworn - Okuno (Black Temple, Shadowmoon Valley)
Scale of the Sands - Indormi (Mount Hyjal, Caverns of Time, Tanaris)
Violet Eye - Apprentice Darius (outside Karazhan, Deadwind Pass)
Koren (behind Attumen, Karazhan)
OtherAldor - Quartermaster Endarin (Aldor bank, Shattrath)
Kurenai - Trader Narasu (Telaar, Nagrand)
Ogri'la - Jho'nass (Ogri'la, Blade's Edge Mountains)
Scryers - Quartermaster Enuril (Scryer bank, Shattrath)
Sha'tari Skyguard - Grella (Blackwind Landing, Terokkar Forest)
Sporeggar - Mycah (Sporeggar, Zangarmarsh)
Wrath of the Lich KingTabard championableArgent Crusade - Veteran Crusader Aliocha Segard (Argent Vanguard, Icecrown)
Kirin Tor - Archmage Alvareaux (Violet Citadel, Dalaran)
Ebon Blade - Duchess Mynx (Shadow Vault, Icecrown)
Wyrmrest Accord - Cielstrasza (Wyrmrest Temple (top level), Dragonblight)
OtherAlliance Vanguard - Logistics Officer Brighton (Valgarde, Howling Fjord)
Logistics Officer Silverstone (Valiance Keep, Borean Tundra)
Ashen Verdict -Alchemist Finklestein (Light's Hammer, Icecrown Citadel)
Frenzyheart Tribe - Tanak (Frenzyheart Hill, Sholazar Basin)
Kalu'ak - Sairuk (Moa'ki Harbor, Dragonblight)
Tanaika (Kamagua, Howling Fjord)
Oracles - Geen (Rainspeaker Canopy, Sholazar Basin)
Sons of Hodir - Lillehoff (Dun Niffelem, Storm Peaks)
CataclysmGuardians of Hyjal - Provisioner Whitecloud (Nordrassil, Hyjal)
Earthen Ring - Provisioner Arok (Silvertide Hollow, Shimmering Expanse, Vashj'ir)
Therazane - D'lom the Collector (Therazane's Throne, Deepholm)
Ramkahen - Blacksmith Abasi (Ramkahen, Uldum)
Wildhammer Clan - Craw MacGraw (Thundermar, Twilight Highlands)
Baradin's Wardens - Quartermaster Brazie (Tol Barad Peninsula)