Jetpack is a new plugin for your WordPress (either .com or self hosted installations) from Automattic, that provides a cool set of features: Hovercards, Stats, After the Deadline, Twitter widget, shortcodes, shortlinks, easy Facebook/Twitter/WordPress sharing buttons and even LaTex.
More features will be available in the future.
You’ll need a WordPress.com account to have it working on your self hosted WordPress blog, but it’s free and you don’t even need to create a new blog.
Although most of these features are available as separate plugins from other developers, Jetpack consolidates all in one, consuming less memory (at least for me) and storing some of the data on the cloud.
Jetpack is available for free and can be downloaded here.