Display Suite allows you to take full control over how your content is displayed using a drag and drop interface. Arrange your nodes, views, comments, user data etc. the way you want without having to work your way through dozens of template files. A predefined list of layouts (D7 only) is available for even more drag and drop fun!
By defining custom view modes (build modes in D6), you can define how one piece of content should be displayed in different places such as teaser lists, search results, the full node, views etc.