Grabbed from Flyertalk, where credit is given to SlickDeals.net, the following coupons are available on Orbitz for discounting hotel stays:

$50 off 3 nights: 50AFFORB [Exp. 12/31]
$60 off 3 nights: VISAVIP [Exp. 8/15]
$75 off 4 nights: 4ODWR75 [book by 12/31, travel by 2/15/09]
$100 off 5 nights: EQUALITY100 [book by 08/31, travel by 11/15]
20% off:7DAYSALE3 [for travel by 10/31]
$200 off 5 Night stay in Hawaii: ORBHI200 [Exp 8/7]
Tips on combining codes: These codes are not “stackable”. But if you wanted to do a longer trip such as a 7 day trip, do two separate transactions. For days 1-3 use code VISAVIP for $60 off 3 nights. Then for days 4-7 use code 4ODWR75 for $75 off 4 nights.
VISAVIP+4ODWR75 = $135 off 7 nights

Say you wanted to a 10 day trip in Hawaii, again do two separate transactions:
ORBHI200+ORBHI200 = $400 off 10 nights in Hawaii
These are for hotel stay only, not valid on hotel+flight packages.

I haven’t checked these out myself, but a reliable source in the Flyertalk thread reports that 7DAYSALE3 is not currently valid.