I've had a lot of success by adding valuable tools that I know my visitors can use. I am in the telephone answering service business. All of my clients use call forwarding, so we provide instructions on call forarding for every telephone company we can find.
I also recently added a tool for sending SMS text messages and vairous pages describing how to send SMS via email and visa-versa.
I was told by someone who knows more than I to always try to deliver relevant value. In the beginning we tried the usual tricks like weather forecasts and recent news. The items I mentioned above increased our organic traffic and more important, reduced bounce backs.