Blogging Pro has a post with 5 Reasons to Use WordPress as CMS.
If you are an experienced user of WordPress (WP) and want to setup a non-blog website - perhaps a portfolio site, news/magazine site or even an e-commerce site - you might just want to skip the more robust content management systems (CMS) most people tend to suggest, like Drupal and XOOPS, and consider using WordPress for your CMS-oriented task instead.
One of the links that you won’t want to miss is to this post with examples of WordPress being used for a non-blog website.