Jetpack

Jetpack is a free WordPress plugin that simplifies managing your sites. This single plugin enables Photon (a global CDN for images), uptime monitoring, brute force protection, traffic-boosting tools, single sign on, multiple-site management, and automatic or bulk plugin updates. Additionally Jetpack includes several features that help you customize the look and feel of your site without installing other tools.

More information can be found at jetpack.com.