The one travel rewards card I'm particularly fond of is the American Express Blue Sky card. It earns a guaranteed 1.33% toward travel on all spending. And its earnings can be applied to any airline, any hotel, any vehicle renter, etc.

If you're not opposed to taking your earnings as cash (which of course can be applied to travel : ) ), other good options open up such as the AmEx Blue Cash card and the Chase Freedom card.

An easy way to see which rewards card will pay you the most for your spending profile is this rewards calculator:
http://www.creditcardtuneup.com/

Note that the tool converts all earnings currencies (frequent flyer miles, points, cash back, etc.) into dollars so you can do an apples-to-applies comparison.