I recommend Hotels25.com for a quick search.
If you have time to search all booking sites separately, I have provided a complete list below:
Further discount often possible with discount codes you can find at Retailmenot.com.
Impressive 7% cashback.
World famous booking site, easy to book. Often run promotions.
Over 110,000 hotels world wide. Coupons often available at Retailmenot.com.
Over 160,000 hotels world wide and high customer satisfaction (Trustpilot)
World famous booking site, easy to book.
Part of TUI Travel PLC with more than 30 million customers worldwide.
Part of Priceline and just recently introduced their own rewards program.
Discount codes often available at at Retailmenot.com.
Only luxury hotels, but the good thing is all hotels are up to a high standard.
Popular hostel site with hostels in over 3.500 destinations.
World’s largest hostel database.
Vacation rentals can be a great alternative to hotels. Worth to check out.
Worth to check out their “Deals of the Day”
Over 250,000 hotels world wide. HRS has a list of newly opened hotels with special opening rates.
More than 5.000 hotels in the most popular destinations around the world.
“11,000 budget hotels in over 1,600 destinations”
Only search engine where flexibility is possible for hotel dates.
Impressive Price Drop Protection™ on all flights, hotels and vacations.
Search engine where you can get special deals when you share a post on twitter or FB. New concept.
Specialists in group bookings.
Earn Air Miles on hotel bookings – Right now: Earn 1.000 miles with your first booking!
Last Minute Travel
Use code htravel1 for $25 off your first stay.
Couchsurfing is a hospitality exchange and social networking website.