Writing used to be an exercise for those who were really into it. With the prevalence of blogs and web sites owned and maintained by the average person, the art of writing has extended to more than those who actually studied for it. Anyone can be a writer these days, but that is not to say that everyone is a good writer.
Whether you are a blogger or you just want to learn how to write better, Dead Mentor is a good blog to learn from. It presents writing exercises, tips, book reviews, and other insights that you will find useful.