Building a community should be one of the most important goals of a blogger. As a blogger, you want to spread your views on various topics and give advice to people; however, to achieve this you need to have many readers. You need to create a blog that will encourage people to join your community. This can be accomplished by writing posts that have some of the following characteristics:
Ask questions in your posts. This is in my opinion the best way to encourage your readers to contribute something to your website. People like to be engaged in a discussion and they like it when someone wants to listen to their opinion.
Give advice to your visitors. Visitors like this, especially if it is useful advice. That is why most of the top articles on Digg or similar websites give some useful advice.
Provide your opinion on something that your readers can add something to. Allow them to express themselves. Make them feel like you actually want to listen to them.
Taking questions from readers and answering them in your post is a good idea as well. Is there anything that you were asked in comments, but did not ever respond for some reason?