Mobile Spell-Casting( Complete Adventurer, p. 111)
Your focused concentration allows you to move while casting a spell.
Concentration 8 ranks,
You can make a special Concentration check (DC 20 + spell level) when casting a spell. If the check succeeds, you can cast the spell and move up to your speed as a single standard action. (You can't use this ability to cast a spell that takes longer than 1 standard action to cast.) If the check fails, you lose the spell and fail to cast it, just as if you had failed a Concentration check to cast the spell defensively. You still provoke attacks of opportunity for casting spells from any creatures who threaten you at any point of your movement. You can cast defensively while using this feat, but doing so increases the Concentration DC to 25 + spell level.