GC Message Bar lets you put a sticky message to the top or bottom of your site.
Memory Load Consumption and db size Usage allows you display your site’s PHP Memory and Database usage in your Dashboard.
BackWPup allows you to backup your WordPress database, files, and more.
Co-Authors Plus allows you to assign multiple bylines to posts, pages, and custom post types via a search-as-you-type input box.
Facebook makes your site deeply social by integrating functionality from Facebook.
Fast Secure Contact Form lets your visitors send you a quick e-mail message and blocks all common spammer tactics. Additionally, the plugin has a multi-form feature, optional extra fields, and an option to redirect visitors to any URL after the message is sent.
Keyring provides a very hookable, completely customizable framework for connecting your WordPress site to an external service.
Yet Another Related Posts Plugin displays a list of related entries on your site and feeds based on a unique algorithm.