• Shield bonuses to AC also apply to the following: touch AC, Ref saves, attempts to resist trip/grapple/bull rush. The bonus to Reflex saves applies only against effects which affect you directly (like fireball), and does not apply against effects which affect you by targeting the area around you (like grease or falling into a pit).
  
• Your shield's enhancement bonus applies to attacks you make with it as a weapon (including "parry" maneuvers). However, a shield bash deals non-lethal damage.
• When you use your shield to make an attack of opportunity, instead of attempting to strike the target you may use the result of your attack roll as your AC/Ref save against the action which provoked the AoO. If you are capable of making multiple attacks as part of an attack of opportunity, this only affects a single attack made with your shield.
• Similar to how two-handed weapons make Power Attack more effective, if you use total defense, Combat Expertise or fighting defensively in conjunction with a shield then the bonus to AC is doubled. You cannot use an animated shield in this manner, since you lack direct control of its movements.
• Combat Expertise is capped at your BAB, and does not penalise attack rolls made to parry.
• Total defense can be combined with Combat Expertise or fighting defensively.

Quote from: Prime32 on November 18, 2011, 08:48:46 AM

• Shield bonuses to AC also apply to the following: touch AC, Ref saves vs area effects
  

Does that include Web and Grease? In my version, it only works against affects that offer a Reflex save for half damage.