Polls are a great way to promote interactivity on your site (voting).
Marty Wall's Fritz Cartoons needed a showcase for his fantastic cartoon work. He needed to be able to upload daily cartoons quickly, easily, and professionally. Meet WordPress.
Pee-in-your-pants-funny satirical newspaper site using quite some WP features: voting, polls, social bookmarks, etc.
BNI Embarcadero's site gives its 60+ members access to members-only information, an automated roster of members, group mailing list software (one-to-all), and many other features that save the organization time and money.