Neo39 and Grey One in Pasadena are tight shops to hit if you are in the area, but they are heavily trafficked, so don't expect to come up on any steals...
not much in the OC area that hasn't been mentioned - Cerritos Mall has all the major shoe chains in one mall: FL, FA, Champs, a huge Finishline, even Athlete's Foot (most other malls out here only have maybe 2-3 of them)... sleeper mall: Montclair mall off the 10 in the Pomona area. If you are hitting the Ontario Mills outlet, Montclair is worth a stop, I've found some nice stuff there because its kinda in boonieville...
malls to avoid in the OC area: Brea, Santa Ana Mainplace, and avoid South Coast Plaza at all costs if you are looking for shoes since all they have is one small Footlocker (if you are looking for authentic Prada, Gucci, Burberry, Armani etc, then this is the place for you - South Coast also gets my prize for the most amazing women per square foot than any place in socal that is not a beach or club)...
if you are looking for dunk SB's, good luck my friends, just because you know of the specific skater/surf shops that carry them, it doesn't mean that when you get there they will have anything at all. And when you call, they often lie about what they have in stock. Its hit-or-miss and the reselling game here is cutthroat so finding anything for cheap is tough. You cna always hit sportie LA if you want to pay an arm and a leg; I'd personally rather hit ebay than pay price-gouge prices...
"...if ya feelin lucky-duck, then press your luck"