If you are financially responsible and can pay off your bill at the end of the mont, there is no reason why you should not be using a credit card. In addition to the rewards programs you mentioned, there are many other perks to credit cards.
-0% Balance Transfers for a lot of cards
-Extended warranties and product protection
-Build your credit
-Insurance on things like Rental Cars, etc
-Charge disputes for crap merchandise, etc
-More protection in the event of a lost/stolen card
The following sites have great listings of credit cards:
http://www.bettercreditcard.com
http://www.indexcreditcards.com
http://www.fatwallet.com/forums/c/52/
If you would make the most use out of frequent flier miles, or points for hotel stays or other travel deals, there are cards for that. If you would rather have cash back, there are TONS of cards for that.
Personally, at the moment, I have many credit cards, and I use them differently depending on the rewards structure.
-Citi Driver's Edge gives me 6% cash back at gas stations, grocery stores and drug stores for the first 12 months (3% after that), and they will double it based on reported miles you drive on your car. I'm effectively getting 12% back at these places for the first 12 months.
-American Express Costco card (if you're a Costco member) gives you 3% at restaurants, 2% on travel purchases, and 1% everywhere
-Chase Freedom gives you 3% on whatever "category" you spend the most on
-Amex Blue Cash gives 5% back on every dollar over $6500
If you pay your bills, and are shrewd with use of your cards, you can get big savings using rewards cards.