Here is a Do It Yourself guide available for download.
http://www.howtocustomizewordpress.com/There are many templates out there as well. You can changes things around in the CSS, but it is much easier if you find a template and tweak it a bit.
And another site explaining customizing WOrdpress:
http://www.problogdesign.com/wordpress/10-ways-to-customize-and-personalize-your-wordpress-blog/