Priceline offers rewards through its branded Priceline Signature Visa card on hotel, rental car, and vacation package purchases.

Accruing points: Travelers get five points for every dollar spent on Priceline's "Name Your Own Price" travel bookings, and one point for every dollar spent on any other purchases made with the credit card.

There's a bonus of 5,000 points when you use the card for the first time or transfer a balance from another card. If you spend $1,000 on the card within the first 90 days, you qualify for another 5,000 bonus points.

Redeeming points: Even if you don't use your rewards for travel discounts, you can apply them as credits on other purchases of $25 or more made with the card.

Expiration: You can use Priceline's points for up to four years.

What makes it a deal: Although Priceline's program offers members a lower rate of return than some of the other sites' programs, members can use their points for discounts on any purchase -- an attractive option, said Kelly.

The 5,000-point rewards are a nice bonus, said Kelly. But the real value of Priceline's service is the savings it offers on hotels, which are still generally better than competitors -- although that gap is narrowing.

The drawbacks: Priceline doesn't give travelers as many points for hotel bookings as some of its competitors.

The APR on the credit card ranges from 15% to 22% depending on your credit history. And while you can earn points when transferring a balance to the card, you cannot earn them when using a balance transfer check. Balance transfers also entail a fee.