Old Navy is having a Flip Flop sale tomorrrow! There are also two great Old Navy coupons:
$5 off a $25 Old Navy Purchase (good through 6/3)
$10 off a $50 Old Nave Purchase (good through 5/27)
These will likely sell out very quickly tomorrow, so I suggest getting there early. There is a limit of 5 pairs of flip flops per person.