After reading the article suggested by Joan I found this fascinating quote within the article:
Every blogger, no matter how ambitious or dedicated to his or her blog - wants a community around it. Easier said than done of course. To build a community you have to get people engaged around the premise of your content and then make it as easy for them to interact as possible. Both with you and each other.ShoutEm, Mar 2009
You should read the whole article.