DVDPlanet.com has 20% off with coupon: 20offsale and it IS reusable. Coupon good through November 21st. This is NOT usable on pre-orders. I've never ordered from these guys, so I can't say what their prices are like.

I also found a list of codes for DeepDiscount. Usually you can only use a code once, so if you need to do a second order these should work. Note this list is not verified! These are the usual codes, and they usually always work. But no guarantees!

DVDTALK
USATODAY
NYTIMES
SUPERSALE
PRICESEARCH
YAHOO
ESPN
XM
JIM
DEALNEWS
DD1109 - Confirmed code
LATIMES
WGN
WLS
PRICEGRABBER