There were tons of articles about Wordpress Plugins, Wordpress Most Useful Plugins, Wordpress Essential Plugins etc. Everyone is trying to create their own list and so do we 
But our list is different, we tried to list only plugins you can use when building a typical business website, where blog is just a part of the website, and not a main feature.
We’re using these plugins on a daily basis, some of them are simply essential for every website (All In One SEO Pack, Google XML Sitemaps, cformsII, Insights, Search Everything), some of them we’re using in particular cases (WP-PageNavi, NextGen Gallery, Flash Video Player) and some we used only once so far (WP AutoSuggest, WP-Syntax, WP-Polls, Twitter Tools).
OK, here’s the list:
Essentials
All In One SEO Pack
All In One SEO Pack is a must-have plugin if you are serious about SEO for your website. It works out-of-the-box so once installed you don’t have to look on it. What it does automatically:
- Automatically optimizes your titles for search engines
- Generates META tags automatically
- Avoids the typical duplicate content found on Wordpress blogs
- You can override any title and set any META description and any META keywords you want.
- And more…
However, if you want it offers you options to fine-tune almost all website parameters that are responsible for perfect Search Engine Optimisation.
Download All In One SEO Pack. Read more about the features.
Google XML Sitemap
This plugin will create a Google sitemaps compliant XML-Sitemap of your WordPress blog. It supports all of the WordPress generated pages as well as custom ones. Everytime you edit or create a post, your sitemap is updated and all major search engines that support the sitemap protocol, like ASK.com, Google, MSN Search and YAHOO, are notified about the update.
Use it carefully though. Long story short, we deployed new Wordpress website on the client’s server but it wasn’t visible to the general public yet. All essential plugins were installed, Google XML Sitemaps as well. Before website was populated with content by the client people were able to find it and use it, especially booking form was used (this is a dental practice website)!
Download Google XML Sitemaps. Google XML Sitemaps Homepage.
cformsII
cforms is a powerful and feature rich form plugin for Wordpress, offering convenient deployment of multiple Ajax driven contact forms throughout your blog or even on the same page. It enables you to create forms and use anywhere on your website. Forms can be as simple as name, email and message or as complex as multiple page surveys. It’s very powerful plugin.
Download cforms plugin.
Insights
Insights it’s a plugin that extends functionality of Wordpress administration panel. Did you ever think about how to easily add interlink between your posts or pages, flickr images, YouTube videos, results of Google searches or Google Maps? If you can answer yes to any of these questions then Insights is a plugin for you. Insights allows you to do all this using dynamic AJAX interface which loads the relevant information to your post in just a few seconds.
A practical example is a website for estate agent who can now illustrate every property on one’s website with detailed location map (the only one disadvantage is that generated map is static).
Search Everything
Search Everything increases the ability of the default Wordpress Search. It includes:
- Search Highlighting
- Search Every Page
- Search Every Tag
- Search Every Category
- Search non-password protected pages only
- Search Every Comment
- Search only approved comments
- Search Every Draft
- Search Every Excerpt
- Search Every Attachment (post type)
- Search Every Custom Field (metadata)
- Exclude Posts from search
- Exclude Categories from search
Useful but not essential
WP-PageNavi
First of non-essential plugins, WP-PageNavi. It does exactly what it says, creates pages navigation you can customize and match with your design. Simple and effective.
Download WP-PageNavi plugin. Read more about WP-PageNavi plugin.
NextGen Gallery
NextGEN Gallery is a full integrated Image Gallery plugin for WordPress with a Flash slideshow option.
- Templates : You can add custom templates for your theme.
- Media RSS feed : Add the Cooliris Effect to your gallery
- Role settings : Each gallery has a author
- AJAX based thumbnail generator : No more server limitation during the batch process
- Copy/Move : Copy or move images between galleries
- Sortable Albums : Create your own sets of images
- Upload or pictures via a zip-file (Not in Safe-mode)
- Watermark function : You can add a watermark image or text
- JavaScript Effect : Use any available popular image effect : Shutter, Thickbox, Lightbox or Highslide
- and even more features…
Download NextGen Gallery plugin. Read more about NextGen Gallery plugin.
Flash Video Player
The flash video plugin for WordPress allows the addition of video (and other media) to a WordPress website using standards-compliant markup and the leading open source software (Jeroen Wijering’s FLV Player and Geoff Stearns’ SWFObject Javascript Library). A full options menu is available with post-level overrides for endless customization. Installation is quick and easy, and no additional setup/coding/php knowledge is required. This plugin is low footprint, creating no tables, and uninstalling cleanly. Version 3 provides full support for skinning the player as well as video player plugins.
You can see it in action here and here (with captions).
Download Flash Video Player plugin. Read more about Flash Video Player plugin.
Special Plugins
WP AutoSuggest
WP AutoSuggest adds the Auto Suggest support to the WordPress search. The visitor can enter a keyword and the plugin will show him a few suggestion via an AJAX request before submitting the search query. The visitor can continue his search by pressing enter or he/she can use the keyboard arrows (up and down) to visit directly a suggested post.
See it in action! Just type anything in the search box at the top of the page.
Download WP AutoSuggest plugin. Read more about the WP AutoSuggest plugin.
WP-Syntax
WP-Syntax provides clean syntax highlighting using GeSHi — supporting a wide range of popular languages. It supports highlighting with or without line numbers and maintains formatting while copying snippets of code from the browser.
It avoids conflicts with other 3rd party plugins by running an early pre-filter and a late post-filter that substitutes and pulls the code snippets out first and then pushes them back in with highlighting at the end. The result is source code formatted and highlighted the way you intended.
Download WP-Syntax plugin. Read more about WP-Syntax plugin.
This is it, a list of essential and not-so essential plugins that we use in almost every project that involves Wordpress. Suggest your essential plugins in teh comments!