We pay our balances in full every month too, and with the cash back rewards cards it's like banks are paying us to use their credit cards. Gotta love that! Most cards offer at least 1% on general purchases but there are ways to get more. Here's what I use to maximize our rewards:
Discover Card--keep track of what the bonus categories are and use it for those purchases. It earns 5% on those (I keep track until I reach the limit, currently it's 5% on up to $400 in purchases at home improvement, department, and clothing stores.)
Target Red Card--only for purchases at Target, saves 5% right on the spot.
Amazon Visa (from Chase)--For Amazon.com purchases (3% back) and 2% for gas stations, restaurants, drug stores, and office supply stores.
Costco's American Express--They currently have a tiered system like the Amazon Visa, but I am still under the old plan of 1.5% on all purchases. I use this card for everything that doesn't fall under any of the other cards' bonus categories. Some merchants don't take American Express, so I use the amazon visa which still earns 1%.
The Chase Freedom Card is similar to Discover with rotating 5% cash back categories. I've got one but haven't been using it much simply because I was getting mixed up between which categories it had the bonus on and which were Discover's. When I get my act together with that, I'm sure I will utilize it more.