Don't pick a web site engine (blog, CMS, or other), unless you have the ability to customize the style. A web site should have the ability to change designs over time as personal preferences, and desired style and color preferences change. Sites using a site builder tool require a lot of hand coding or a complete re-generation of the site. This can add additional cost or time to customize. Sites that use a theme engine can be modified or changed quickly with minimal cost or time.
For a better example of what theme switching can do, see Themes Galore.
Engines that use a theme engine to allow quick styling and deployment include the following.
For a more extensive list of Content Management Systems (CMS), refer to the post on 50 Content Management Systems.
Some of the more interesting CSS templates, or themes I've seen are listed below. These themes include the CSS and the templates uses for posts, pages, headers, footers, etc.
Tags: Free themes, CSS templates, Wordpress themes, XHTML templates