The Author Image plugin for WordPress adds widgets that let you easily add author images on your site.
The Auto Thickbox plugin for WordPress automatically enables thickbox on thumbnail images (i.e. opens the images in a fancy pop-up).
The Bookmark Me WordPress plugin lets you display subscribe links to social sites such as Facebook, Google+, Twitter, and Pinterest.
The External Links plugin automatically marks outgoing links as such.
The XML Sitemaps WordPress plugin automatically generates a XML Sitemap files for your site and notifies search engines when they're updated.