JOINCLUBRT
This site has often been recommended by OzBargain members but I just got a chance to check it out. Here and here.
lmtclub.com (this normally costs US$50 to join, but there are free membership codes floating around; has good rates for certain hotels, particularly in the US).
Not a huge difference in NZ hotels but can be pretty big for US hotels. Also, really good for discount theme parks in the US.
Best to play around with the site and see how it compares. Prices are in USD so comparisons are also in USD. My sample bookings (Feb 7/8):
Grand Chancellor Auckland
Hotelscombined - $152 NZD ($US118.66) -Hotelpronto
LMTClub $132 NZD (Converted) - $102.92USD
—
Intercontinental Wellington
Hotelscombined - $503 NZD ($US392.25) -Hotelpronto
LMTClub $495 NZD (Converted) - $386.18USD
—
Doubletree Metro NYC (Nov 7/8)
Hotelscombined - $256.25 USD via Hotelsclick
LMTClub - $220.08
—
Palazzo Las Vegas(Nov 7/8)
Hotelscombined $295 USD via Skoosh
LMTClub - $253.95 USD
(Note: I tested these prices last month so pricing has probably changed.)
Credit to MITM and Fatwallet. Fatwallet members don't recommend using it for flights, just hotels.
Shop around a bit. You might be able to do better with using coupons with hotel sites. Also check out the OzBargain Travel wiki.