If you self-host a WordPress blog, one of the most useful plug-ins you can install is Jetpack, created by WordPress publisher Automattic originally for blogs built on the hosted WordPress.com service

The Jetpack plug-in has recently been updated to version 2, which now makes it an indispensible part of your blog presence on the social web.

Jetpack offers a huge range of features, services and functionality that enhances your WordPress experience – both yours as the content publisher and those who interact with your content.

With version 2, Jetpack currently brings nearly two dozen modules that you activate to use in your WordPress site.

Once you install the plugin, it created a dashboard in your WordPress admin through which you manage all aspects of it.

You will need an account at WordPress.com even if you don’t have or plan to have a blog there, as the plugin connects with data and services in the WordPress cloud. Opening an account is free of charge.

You use the Jetpack modules you want, which may not be all of them. I have some activated, not all; the ones I find very useful are these:

• Comments: enables your visitors to use WordPress.com, Twitter, or Facebook accounts when commenting on your site.
• Subscriptions: Allow users to subscribe to your posts and comments to receive a notification via email.
• Contact Form: Easily insert a contact form any where on your site.
• Sharing: The most super duper sharing tool on the interwebs. Share content with Facebook, Twitter, and many more.
• Shortcode Embeds: Easily embed videos and more from sites like YouTube, Vimeo, and SlideShare.
• WP.me Shortlinks: Enable WP.me-powered shortlinks for all of your Posts and Pages for easier sharing.
• Mobile Theme: Automatically optimize your site for mobile devices.
• Enhanced Distribution: Share your public posts and comments to search engines and other services in real-time.
• Custom CSS: Customize the appearance of your site using CSS but without modifying your theme.

I’ve dispensed with other plugins where Jetpack offers similar or better functionality. It’s definitely a core plugin that will give any self-hosted WordPress blog a boost.