The author says; “Network Blog Manager aspires to be the perfect companion of every Super Administrator of a WP Blog’s Network.
Thanks to its internal search engine, Network Blog Manager helps you find easily every blog in your network. For each blog, you can then contact the administrator and have a quick overlook of the related contents (posts, pages, comments).
Network Blog Manager is extensible: you can build your own functionality thanks to internal plugin support!”
Download and info: http://wordpress.org/extend/plugins/network-blog-manager/