At the end of my love-hate story with MBNA, I put a footnote saying I will discuss how to get $1,000 just by taking advantage of credit card promotions. After sharing many of my experiences using credit and credit cards especially, I believe it helps to put together a summary of the best deals that are around.
First, Citi® Dividend Platinum Select® Card should be in everyone's pocket. This card offers 5% cashback on supermarket (grocery store), drugstore and gas station purchases and 1% cashback on everything else, up to an annual limit of $300. Potential Gains: $300/Year, if you spend at least $500/month in grocery or gas refilling.
Second, try MBNA's recent promotional offer on its MBNA Cashback Card. That offer gives 10% cashback in terms of statement credit for grocery store, drugstore, restaurant and home improvement store purchases and 1% cashback on everything else, up to a month cap of $25. Potential Gains: $250 until the end of the promotion (6/05), if you can spend another $250/month on grocery shopping, dining out or hardware.
Third, get another flat-rate cashback card with no annual cap. If you have a Fidelity investment account, I recommend its 1.5%-flat-cashback Fidelity Investment Rewards® MasterCard® or 2.0%-flat-cashback Fidelity Investments 529 College Rewards Card. (If you don't have Fidelity account, pick up any 1% flat cashback card -- there are plenty of them.) If you regularly spend $2,500/month on credit card purchases, you should expect at least $20-$30 every month even after you divert some expenses to more rewarding cards mentioned earlier. Potential Gains: $300+/Year.
These low hanging fruits can easily give you $850 in twelve months. If you work a bit harder, snatch the 15,000 MileagePlus miles (worth $150+), take advantage of some 0% APR offers (another $75 for me) and get up to $165 quick cash when you play with Citi in its Credit Protector Program. 
Adding these numbers together, I am on track to get $1,240 credit card earnings.
If I write like many personal finance columnists, I will go ahead and say if you deposit this $1,240 into a retirement account every year, and your money earns you an annual return of 10%, in 47 years you will be a millionaire just by clever credit card picking. Sounds really cool?