What is a WordPress Plugin?
Plugins can extend WordPress to do almost anything you can imagine. WordPress Plugins allow easy modification, customization, and enhancement to a WordPress blog. Instead of changing the core programming of WordPress, you can add functionality with WordPress Plugins. WordPress Plugin is a program, or a set of one or more functions, written in the PHP scripting language, that adds a specific set of features or services to the WordPress weblog, which can be seamlessly integrated with the weblog using access points and methods provided by the WordPress.
 Akismet Spam Killer
You would definitely not like to see people selling ‘Viagra’ and other unwanted stuff on your blog. If you wish to stop all these incoming SPAM links/comments, then you must turn on this Plugin. WordPress have this Plugin pre-installed; you just need to turn it on in your Admin panel. You need this because you have better things to do with your life than deal with the underbelly of the internet. Automattic Kismet (Akismet for short) is a collaborative effort to make comment and trackback spam a non-issue and restore innocence to blogging, so you never have to worry about spam comments.
 Google Sitemaps
This Plugin help index your blog in search engine instantly when you publish a post. It also sends auto pining to Technorati, notify Google Yahoo! and other search engine like askme.com. You must install this Plugin if you want your WebPages to be found by Google right away. The Sitemaps protocol allows a webmaster to inform search engines about URLs on a website that are available for crawling. A Sitemap is an XML file that lists the URLs for a site. It allows webmasters to include additional information about each URL: when it was last updated, how often it changes, and how important it is in relation to other URLs in the site. This allows search engines to crawl the site more intelligently.
 Viper’s Video Quicktags
This is the third most important WordPress Plugin that I would like recommend to you. This Plugin is used for inserting video in your blog post from various video hosting sites like YouTube, Metacafe etc. It will save your time if you are tired of copying and pasting the embed HTML codes from video hosting sites like YouTube, Vimeo? Just simply click one of the new buttons that this Plugin adds to the write screen (rich editor included) and then paste the URL that the video is located at into the prompt box — easy as that. You can fully configure how the videos are displayed (width, height, colors, alignment on the page) and much more. Your site will even stay (X) HTML valid unlike with the code provided by most video sites.
 All in One SEO Pack
If you are not an expert in SEO (Search Engine Optimization) you must use this Plugin which help you rank better in Search Engine Results. All you have to do is to fill some parameter after installing this Plugin like explained in the picture below. This allows you to easily edit and control the Title, Meta description, and Meta tags for each post you write. This is very useful because WordPress by default will use your blog tagline as your Meta description and keywords. The keywords in your tagline won’t have a positive effect on all of the keywords for all of your posts because they won’t describe to the search engines what is found within the content of your posts. You can customize each post on your blog for maximum search engine results. This Plugin is streamlined for some best practices for WordPress SEO. While it gives you many options, the defaults reflect the settings. Given below is a list of the most important on-page ranking factors and how they are addressed by WordPress SEO Plugin:
· If your post titles don’t contain your most precious phrases you want to rank for, then tweak them. Leave the post titles as it is but change the Meta title.
· If you don’t want to invest the time and write a description for every post, at least let them be auto-generated. The preferred source for your post description is your post excerpt. Use this when you want to tweak your description.
· All in One SEO Pack can generate keywords from your categories. Using your categories is optional, the rest is autodetected and used.
· You can have “noindex” and the like generated for archive-, category- and tag pages if you seem to have trouble with duplicate content.
 Ninja Affiliate WordPress Plugin
Well Ninja Affiliate is a WordPress Plugin which can do that for you. All your blog posts that lay idle and all those keywords that you wanted to link can be made affiliate links instantly, that can earn you passive commissions. Within a second you can convert keywords like Themes, Plugins, etc. to your affiliate links. The reason being- you have those keywords already linked with the affiliate link and it is going to stay right there. This means you will be the earning commissions even if someone reads that post after say, 5 months or 8 months. Now, think about all the hundreds of blog posts lying idle on your blog. Don’t you want to earn from them lifelong? Making money from blogging is not easy; people find it really difficult and hard to earn enough money even to payout their monthly internet charges and hosting charges. The reason on the other hand is pretty simple. Your blog is not fitted with some power packed tools which are necessary to make your blog a money making machine. That is why I am recommending this lethal weapon to be fixed in your WordPress Blog.
 OIO Publisher Plugin
Since the time I fitted this Plugin on my blog, I know how magnificently it has changed the way I tried to sell ads on my blog. It handles most of the private ad selling part automatically. An advertiser can book ads, upload ad banner and make the payment through your OIO Publisher purchase page. OIO Publisher WordPress Plugin that manages your ad spaces your Text Link Ads, Banner ads, Inline Ads, Paid Reviews and any types of ad spaces you can think of by displaying the ads on the designed section of your website or blog automatically. The best part of OIO Publisher is that it can transform your WordPress powered website or blog into an ad server – managing your advertising clients on your network of websites and blogs in one single place. Here are some cool features which OIO Plugin offer:
· OIO can be used as a standalone platform, or as a WordPress Plugin
· Sell text ads, banner ads, in-content ads and paid reviews
· Sell custom items; from custom ads to digital downloads
· Entirely automated; purchases and expirations all handled automatically
· Click and Impression tracking and weekly ad reports emailed to advertisers
· Ad status management; approve / reject / expire / renew / validate a
· Setup your own affiliate program; reward people for selling your ads
 Sociable Plugin
Sociable is a Plugin which adds social media buttons to your posts, and does so easily, and beautifully. It’s very useful and I recommend you to install this on your WordPress blog. If your reader likes your post then he can instantly share your post on various social media sites like twitter, facebook, MySpace etc with the help of this onderful Plugin.