I think it really depends on what you are marketing (service vs. tangible product). But in a more general case, one really efficient way is to advertise on the side bar. Although it'll cost you a bit but in the end it'll be effective marketing!
you can post your ad through Facebook itself or you can check out one of the ads API tool vendors. One of them is adSage for Facebook. It lets you create, bulk edit, target your audiences and has detailed reporting.