Recently we spent a lot of money on car rental and hotel because of preparing for moving, and I saved a lot of money by using these two websites...
If you use its "bid" function, you will be able to find a very good price for hotel...car rental...etc.
For example, today I just booked a car for $12/day from this website. You may also find a 3-star hotel for $30 here.
Here you can find coupon code for many companies. It is especially useful when you do online shopping. Last month I used this website to book a car from Hertz for 40% off!