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. Chat rooms need moderators, or at least personalities who are interesting enough to keep conversations going. I mean discussions.
Classified sections have to be maintained and cleared of bogus ads.
Polls need to ask relevant questions and provide results on line for everyone to see. Newsletters should be cataloged on the site after they've been sent, building yet another resource for your visitors. When users send you comments, publish them from time to time and carefully consider suggestions they make - after all, they're the ones you built the site for in the first place. And don't tarnish your site's reputation by spamming your subscribers or casual site visitors. Don't make it more of an effort to use your site than it's worth by requiring registrations for everything you offer.