Most people know the rule; Any work that you create is automatically protected under copyright law as being yours. But should you bother to establish your work as copyrighted? The answer is a resounding "YES," according to Sarah Bird, who has written an excellent article on the subject over at SEOmoz.org, with far more legalease than I could ever go into. The basic difference between assuming copyright protection and establishing copyright protection is this: When you assume copyright protection and someone steals your work, you might have a long and expensive court fight just to establish your claim. If you register your work, then your copyright claim is established and you can make the copyright laws work for you; you are eligible to collect statutory damages, including recovering your court costs and attorneys' fees.
There are two components to registering your copyrighted work. The first is to give notice that your work is copyrighted. You'll see in the footer of this web page a standard notice of copyright that most business websites have. What this does is it removes from the defendant the excuse of accidentally or unknowingly pilfering your stuff. Secondly, you can get all the documents to register your copyright at the US Copyright Office online. The cost is $45, so it's probably not something you want to do for every blog entry. But, for original content that may be a key draw for your site, you might want register it. It's not difficult, and you probably don't need a lawyer, though be sure and read Sarah's article for more details on how to write it up.