I noticed that Paladin's Divine Grace is stacking Crusader's Indomitable Soul (Tomb of Battle)
Code:
Indomitable Soul (Ex): Beginning at 2nd level, you draw upon the power of your unwavering faith to steel yourself against the enemies you face. Your personality, energy, and dedication to your faith make it possible for you to shrug off attacks that target your willpower.
You add your Charisma bonus (if any) as a bonus on Will saves. This bonus does not stack with that from a paladin's divine grace ability.