Check out this post from HackADay.

How do you protect your own blog from getting hacked? There’s never a foolproof answer, but with some added tools and caution, you can make your website a little safer from getting into harm’s way. Cats Who Code has five plug-ins and tips you can use to protect your WordPress install. Some of the tips are common sense advice that can apply to anything related to technology – such as making backups often and using strong passwords. Others include suggested plugins that can help you verify whether your WordPress install has any security holes, or small tricks to hide the version of WordPress you’re using. Do you have any useful plugins or tricks to share to keep your blog safe from hackers?