Hotels.com (part of the Expedia combine) has 10% off bookings at:
Use code HCttSPG10
Bookings must be made by May 8 2011 and the discount is valid on so-called ‘Low-Price Guarantee’ hotels.
Bookings at the major chains (Hilton, Marriott, IHG, Accor) are excluded, and full Ts&Cs are available at:
Past experience suggests that these codes sometimes get ‘used up’ before the book-by date, so the Ts&Cs may not be absolutely binding.