Add forums to open up topics for discussion. Forums can be moderated or open and allow your visitors to communicate with you and the rest of the world.
Keep your visitors up-to-date by periodically sending out a newsletter. Your visitors will be able to sign-up to receive your newsletter anywhere on your site.
Add a Blog to your website. Keep your visitors updated with articles that you post on your schedule. Get user feedback by enabling comments on posts to find out what your users are thinking.