Blogs
Keeping your site up to date with your latest news is a great way of turning occaisional viewers into regular viewers.
Blogging tools can also include some effective features such as a comments system to allow viewers to give immediate feedback, enabling a community environment.
You can also use blogs to create an archive of searchable articles that search engines would love you for.
Tagging systems can also be used to help link similar blog entries together in a systematic manner.
And for maximum effect, adding social bookmarking links (such as Delicious, Digg, Stumbleupon and Reddit) to your blog entries enable you to enhance the full power of instant word of mouth.