(MONEY Magazine) – Cash is king, at least where credit-card rebates are concerned. After all, unlike frequent-flier miles, cash back is a sure bet and pays off within the year; no wonder Discover and Private Issue topped all other reward cards in a recent J.D. Power & Associates customer satisfaction survey.

Even as cash-back pioneers such as the GE Rewards MasterCard or Private Issue are capping rewards or making them tougher to earn, more new issuers are wooing cardholders with the lure of cash. "Over the past few months, cash back has been one of the biggest reward cards we've seen tested," says Marcia Waite, president of Market IQ, a firm that tracks card solicitations.

If a cash-back offer shows up in the mail, check to see how much you'll have to charge to earn the top rebate--most issuers tier the rebates based on how much you spend a year--and when the cash dries up. Forget cash-back cards if you carry a balance: Their above-average interest rates of 16% to 20% easily drown out any reward. Take, for example, the Associates Student Card, which is aimed at college kids. The card pays 3% cash back, but only if you carry a balance. Revolve $2,000 a year, and you'll earn $60 and--at today's rate of 17.99%--pay $360 in finance charges.

With these caveats in mind, here's the best of what's available. Unless otherwise noted, none have annual fees.

If your monthly charges rarely hit $1,000, go for a card that gets you to the highest rebate tier the fastest, such as the GE Rewards MasterCard (800-437-3927). You start with 0.5% cash back, earn 1% after your total charges reach $2,000 for the year and work your way up to the top 2% rebate on whatever you charge over $6,000. Rebates halt after you've earned $135, which happens at $10,000. While the card technically doesn't have an annual fee, you'll pay a $25 "user fee" if you don't shell out that much in finance charges each year, so the maximum annual payout is really $110.

If you're unlikely to charge even $2,000 in one year, consider the First USA New York Life Visa (888-200-1716), which pays 1% after you've spent just $500. Although the card is marketed to New York Life customers, anyone can apply.

What if you're a heavier spender? The New York Life Visa and the next two cards, all of which have either generous reward caps or none at all, beat GE if you spend at least $1,200 or so a month on average. The original cash-back card, Discover (800-347-2683), doesn't cap rewards and pays its top 1% rebate after you've charged $3,000 for the year. Discover's sister card, Private Issue (800-474-2273), should be your family favorite if you charge at least $12,900 a year. Its payout jumps to 2% after annual charges reach $12,000, but it will take that extra $900 to make up for the card's $18 fee.

Cash back also shows up in some surprising places. If you're an AT&T phone customer, consider the cash-back program available on any at&t Universal MasterCard or Visa (800-423-4343). If you spend $25 a month on long distance and let AT&T combine your phone and credit-card bills, you'll earn 1% cash back on all purchases. Add wireless, and the rebate jumps to 2%. The U S West MasterCard, issued by Household Bank (888-879-3782), pays up to 2% cash back on purchases and 25% back on calling-card services, up to $500 a year. You'll likely choose the Citibank Driver's Edge MasterCard or Visa (800-967-8500) for the 1% rebate (up to $500 a year), good toward the purchase of a car; but if you haven't used the rebate in five years, you can take it in, yup, cash.

--SARAH ROSE