Sources: Complete Arcane
You learn an additional spell.
Prerequisite: Caster level 3rd.
Benefit: You learn one additional spell at any level up to one lower than the highest level of spell you can currently cast. Thus, a 4th-level bard (maximum spell level 2nd) gains either a new 0-level or 1st-level spell known with which to expand her repertoire. For classes such as wizard that have more options for learning spells, Extra spell is generally used to learn a specific spell that the character lacks access to and would be unable to research.
Special: You can gain this feat multiple times. Each time, you learn a new extra spell at any level up to one lower than the highest level of spell you can cast.