What is the best rewards credit card?

I don't want to pay an annual fee – are there any good free ones?

Citgo Preferred Visa issued by Citibank: 1% cash back on all purchases, credited automatically to your statement the same month.

Chase PerfectCard: 1% back on all purchases, 3% back on gas. Credited automatically to your next month's statement. Uncapped.

AT&T Universal card issued by Citibank, Citi Dividend: 1% back on all purchases, 5% back on purchases at grocery stores, gas stations and drug stores. Limit $300 in cash back per calendar year. Once you have accumulated at least $50 in cash back, you can call or request online a check for the current cash back amount.

Chase Cash Plus: 1% back on all purchases, 5% back on grocery store, gas and drug store purchases. Call or request online a cash back check in $50 increments. Limit $300/year.

American Express Costco TrueEarnings card: 1% back on all purchases (including costco purchases), 2% back on travel purchases (airfare, hotel, rental car), 3% cash back on restaurant purchases. At the end of the year (in Jan/Feb) you get a costco gift certificate which you can use for costco purchases, or you can bring it into costco and redeem it for cash.