Are we talking mechanical similarity or flavor similarity?
Barbarian = Wildshape Ranger, Warblade, Totemist
Bard = Bard, Beguiler, Incarnate
Cleric = Incarnate, Crusader, Ardent
Druid = Wildshape Ranger, Totemist
Fighter = Warblade, Psychic Warrior
Monk = Swordsage, Psychic Warrior, Incarnate
Paladin = Crusader, Psychic Warrior, Incarnate
Ranger = Binder, Totemist, Swordsage
Rogue = Beguiler, Bard, Swordsage
Sorcerer = Dread Necromancer, Beguiler, Binder
Wizard = Dread Necromancer, Beguiler, Psion