Priceline.com is able to offer these deals as part of its "Name Your Own Price" program. The company said it can do the deals because its rental car partners are offering lower rental car rates in certain markets. But as they say in the disclaimer, certain restrictions do apply.

And to participate, you book before you find out what company you rent from, so some people don't like the surprise. Some of the rates available include Denver $15 a day; Milwaukee, $13 a day; Memphis $16, Seattle mid-size, $15. A car in Honolulu could be had for $16 a day.

To qualify for the special savings, priceline.com customers have until Sept. 30, 2007 to purchase and pick up their rental car. Drivers must be 25 or older. All offers are subject to standard rental car requirements and restrictions.