In its most basic form, you can simply set up a form that the user fills in, providing you with an email address for future contact and maybe a box for comments. In more complex situations you might need to set up a database-driven form for your site or sign up for a list server. After email, chat is the most popular online past-time. Or check with your site host. Chances are they offer a chat room package for a nominal fee.
Many Web hosts provide message applications.
There are also applications written in ASP, Java and ColdFusion which are completely customizable by the licensed owner. Create a few key topic areas, recruit a friend or two to help monitor the activity and clean out the dead conversations and presto, you have an instant traffic source as people read and write messages day after day. As long as your user policies are clear and concise and enforced, classifieds are a valuable user service that can provide you with a measurable return on your investment. Imagination is the prime requisite for online contests. Keep up the Good Work Don't expect your community to be self-sustaining, however.