One example would be Eugene Mirman, who is a comedian, and one of the funniest people on Twitter that I know. Following him on Twitter makes you want to consume more of his other content (CDs, books, live shows).
Some other tips would be to grade your website using the free WebsiteGrader tool, and grade your Twitter profile using TwitterGrader - both of these tools will give you some advice on how to improve your online presence. - Mike Volpe, VP Inbound Marketing, HubSpot