This first release of Idealien Category Enhancements (ICE) allows you to manage category templates as easily as you manage page templates. Select which template applies to a category through the post > categories menu using file names that make sense, not category ID numbers. Now any views of the category (or sub-categories) will render the according to the category template selected. Posts in a given category can also use a category-based template. Read this post for complete installation and configuration instructions.