Here's a couple
Fighting Defensively
Draconic Defender feat (Dragon's Revisited): During your action, designate an ally within your reach. When you fight defensively or use Combat Expertise, your ally gains a natural armor bonus to AC equal to the dodge bonus you gain from fighting defensively or Combat Expertise.
Osyluth Guile feat (Cheliax, Empire of Devils): While you are fighting defensively or using the total defense action, select one opponent. Add your Charisma bonus to your AC as a dodge bonus against that opponent's melee attacks until your next turn. You cannot use this feat if you cannot see the selected opponent.
Acrobatics skill: If you have 3 or more ranks in Acrobatics, you gain a +3 dodge bonus to AC when fighting defensively instead of the usual +2, and a +6 dodge bonus to AC when taking the total defense action instead of the usual +4
Flanking
Outflank Feat (Advanced player's guide): Whenever you and an ally who also has this feat are flanking the same creature, your flanking bonus on attack rolls increases to +4. In addition, whenever you score a critical hit against the flanked creature, it provokes an attack of opportunity from your ally.