WordPress is a great blogging platform with a potential of being an easy to use content management system.

WP-CMS Post Control Plugin
This plugin gives you complete control over your write options. It not only allows you to hides unwanted items like custom fields, trackbacks, revisions etc… but also gives you a whole lot more control over how WordPress deals with creating content! This helps you use WordPress more like a CMS, alowing you to totally customise what your authors see and use.

Role Scoper Plugin
Role Scoper is a comprehensive enrichment for access control in WordPress, giving you CMS-like control of permissions. Assign reading, editing or administration roles to users or groups on a page-specific, category-specific or other content-specific basis.

Wordpress Navigation List Plugin
The plugin gives you the ability to create unique site navigation from your pages, categories and users using a Drag ‘n Drop Interface; arrange the items within a group in any arbitrary order. Navigation groups may be composed of any combination of pages, categories, Authors, (Editors, Contributors, Subscribers), internal/external links and list dividers. This plugin has a lot of other great features, you have to check it out.

xLanguage Plugin
xLanguage is a full featured plugin allows you to blog in different language, and allows user to select which version to read. It works for blog post, page, tags, categories. The user language preferences will also select the right theme and plugins MO files.

All in One SEO Pack Plugin
Optimizes your Wordpress blog for Search Engines: page titles, meta tags, keywords, and descriptions. This plugin allows you to configure them for either your entire blog or on a post by post basis.

NextGEN Gallery Plugin
NextGEN Gallery is a full integrated Image Gallery plugin for WordPress with a Flash slideshow option. It can turn a regular blog into a powerful photo-blog while giving you all the tools to manage it efficiently and easily.