The only problem with Able Learner is you have to be either a human or doppleganger, and it can only be taken at first level. I would reccommend the following feat from Complete Champion, myself.
Knowledge Devotion:
You can use your knowledge to exploit your foes' weaknesses and overcome their strengths.
Prerequisites: Knowledge (any) five or more ranks.
Benefits: Upon selecting this feat, you immediately add one knowledge skill of your choice to your list of class skills. Thereafter, you treat that skill as a class skill, regardless of which class you are advancing in. In addition, whenever you fight a creature, you can make a knowledge check based on the creature type, as described on page 78 of the PHB, provided you have at least one rank in the appropriate knowledge skill.
You then gain an insight bonus on attack and damage rolls against that creature type for the remainder of the combat. The amount of the bonus depends on the result of your knowledge check, as follows.
15 or below, +1
16-25, +2
26-30, +3
31-35, +4
36 or higher, +5
You may only make one knowledge check per creature type per combat. If you fight multiple types during the same combat, you may make one check per creature type, possibly gaining different bonuses against different creatures.
Example: Alhandra faces a black dragon, a vampire, and a beholder. She has Knowledge Devotion feat, and ranks in both Knowledge (arcana) and Knowledge (religion). At the begining of the battle, she makes a check to gain bonuses against the dragon and the vampire, but since she possesses no ranks in Knowledge (dungeoneering), she has no chance to gain bonuses against the beholder (an Abberation).
Alhandra's Knowledge (arcana) check grants her a +3 circumstance bonus on attack and damage rolls against the black dragon. Later, a half-dragon enters the fray. Alhandra cannot make another check since she's already checked for the dragon type this combat, but she can apply the +3 insight bonus to her attack and damage rolls against the half-dragon as well
This benefit is an extraordinary ability.