Simple Google Connect is a framework and series of sub-systems that let you add any sort of Google based functionality you like to a WordPress blog.
WP Coming Soon adds a coming soon page with a countdown clock.
Email Log allows you to log all emails that are sent through WordPress.
Keyring provides a very hookable, completely customizable framework for connecting your WordPress site to an external service.
Social Login for WordPress lets your users log in and comment via their accounts with popular ID providers such as Facebook, Google, Twitter, Yahoo, Live, and over 15 more.