A simple question : Do shield bonuses to AC from different sources stack ? for example a fighter with a buckler and 2 weapons (with the feats improved buckler defence and two weapon defence) or an abjurant champion with a hand-shield and the spell shield.
The SRD said:Shield Bonus
A shield bonus improves Armor Class and is granted by a shield or by a spell or magic effect that mimics a shield. Shield bonuses stack with all other bonuses to AC except other shield bonuses. A magic shield typically grants an enhancement bonus to the shield's shield bonus, which has the effect of increasing the shield's overall bonus to AC. A shield bonus granted by a spell or magic item typically takes the form of an invisible, tangible field of force that protects the recipient. A shield bonus doesn't apply against touch attacks.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.