Visitors like to do things on websites, if your website allows your visitors to do something interesting or useful, there is a good chance they will bookmark your site and come back.
What you offer them to do is going to depend a bit on the type of site you have and the type of visitors you attract.
There are a number of website scripts you can get if you want to build something interesting. There is a good resource for website scripts at www.easy-scripts.net
They offer a variety of website scripts from a unique memorial script to a yahoo answers style question and answer script to a fun joke script and a guess the stars script. So you can get the type of script that will fit well with your site. They are all very reasonably priced.
A good one for marketers is at www.searchengine-submission-script.com where you can purchase a script that will allow your website visitors to submit their websites to search engines for indexing. That is the kind of thing people will come back to your site for.
