Blogs are a great (and cheap) way to tell the story of your business, connect with your customer, and cultivate a long-term customer relationship. For you blog to be effective, it needs to be fresh and have some value to your reader. This blog post, "18 Blog post ideas for any small business", on the Small Biz Survival blog provides some ideas for posts that will help you past your blog writer's block.
And if you are wondering, yes -- I used idea number 18 today!