you can get an extra 10% off of sale items with the coupon code "SUPERSALE" but i'm not sure when it expires.
also, they've got a $10 dollar coupon if you complete a survey for them about their site redesign and some of their new products. it only takes a few minutes.
the system wouldnt let me apply both coupons at once, so i emailed customer service to get them to apply the survey coupon. i'll report back on whether or not you can combine the two.
update: the initial response is that unfortunately you can only apply one promotion code at a time.