If you’re looking to modify the look and feel of SharePoint 2010, these links will help you navigate the main CSS classes you’ll want to change…
http://erikswenson.blogspot.com/2010/01/sharepoint-2010-base-css-classes.html
http://eschrader.com/
http://jassimkhan.blogspot.com/2010/04/branding-in-sharepoint-2010-css-classes.html
