A list of subclasses which have appeared in WotC playtest packets, or which are mentioned in Wotc articles. Did I miss any?
Fighter
•Warrior
•Gladiator
•Hexblade
•Knight
•Samurai
•Scout
•Warlord
Cleric
•Life Domain (The Lifegiver)
•Light Domain (The Lightbringer)
•War Domain (The Warcaller)
•Death (The Reaper)
•Protection (The Protector)
•Magic (The Arcanist)
•Thunder, Lightning, and Storms (The Stormcaller)
•Trickery and Thieves (The Trickster)
•Knowledge Domain
•Nature Domain
Rogue
•Thief
•Assassin
•Shadowdancer
•Vagabond
Mage
•Wizard (with specialists in each school of magic)
•Sorcerer
•Warlock
•Psion
•Artificer
Ranger
•Dragon Slayer
•Horde Breaker
Barbarian
•Berserker
•Totem Warrior
Druid
•Circle of the Land (CoastDruid, Desert Druid, Forest Druid, Grassland Druid, Mountain Druid,Swamp Druid, Tundra Druid)
•Circle of the Moon
Monk
•Path of Mercy
•Path of the Phoenix
•Path of Four Storms
•Path of Stone's Endurance
•Path of the Four Elements
•Path of the Open Hand (I didn't look to see if this is the new name for one of the earlier playtest paths)
Paladin
•Oath of Devotion
•others?
Bard