While WordPress offers almost every functionality you need for running a blog, there are a few things missing when using it as a Content Management System (CMS) for a corporate website. The following plugins are considered must haves (by me) because they provide various functionalities which contribute to a successful website but do not come with a standard WordPress installation.
Add Meta Tags - A website, unlike a blog, needs different meta data (such as description, keywords) for different pages of the site. Add Meta Tags plugin automatically adds the description and keywords meta tags to the home page and to single pages based on excerpt and they can also be overridden by creating custom fields.
Google Sitemap Generator - When you are using WordPress as a CMS, you would want to make sure that every page on your site gets indexed by search engines. This is when Google Sitemap comes in. The Google Sitemap Protocol allows a webmaster to inform search engines about URLs on a website that are available for crawling. (Ref: Wikipedia) Google Sitemap Generator plugin automatically creates a google sitemap in XML format. This plugin also notifies Google whenever the sitemap is updated and therefore helps search engine crawlers to perform a better job.
Advanced Search - While WordPress comes with a built-in search functionality, it does not handle complex requests such as boolean search, search within a category, search for exact match which are necessary for a corporate website. Advanced Search plugin, on the other hand, offers intelligent search which allows words searching (not character strings), combination of search operators (eg: +apple -tree), search scoping (based on categories, period), sorting, and more.
WP-Cache - If you website has many pages and receives a lot of traffics, you might like to start using a caching method. WP-Cache is an extremely efficient WordPress page caching system that makes you site much faster and responsive by caching pages in a static file for future requests rather than querying from the database and processing a request each time. The plugin gives you the ability to view and delete cache files and also allows you to customise settings such as expiration time.
WordPress Membership Plugin - WP Members is a feature packed WordPress Membership Management Plugin allowing anyone to turn a WordPress Blog into a fully functioning members site which can accept payments through Paypal, ClickBank and WorldPay. This plugin comes with features such as Multiple Membership Levels, Pay Per Post Access, Partial Content Display, Download Manager, Subscription Length Control and Secure RSS With Tokens. Currently priced at $59.00.
[tags]cms, content management system, software, wordpress, plugins, plugin[/tags]