For those with Citi Dividend Credit Cards, Citi is offering a promotion in which you can earn 5% cash back on purchases made at Department, Electronics and Apparel Stores with your Citi Dividend Card for 3 months once you activate this offer. I just checked my Citi account, and activated it. When you log in, select the "Special offers" link under the "Manage Your Account" menu. It may not be available for everyone, but most people on this SlickDeals thread are reporting success.
For those who don't have a Citi Dividend Credit Card, I don't know if this will be available if you sign up for this card. You can qualify for 6 months of 5% cash back for purchases at supermarkets, drugstores, gas stations, convenience stores and utilities. After the first six months, the cash back is 2%. All other purchases earn 1% cash back. Here's the promo page link.