Blog Majordomo displays a customizable scrolling message in the sidebar to blog readers.
Link Summarizer creates a list at the end of a post of all the link referred to in the post itself. The plugin can be configured in the admin to exclude certain links from the link summary.
Mabber sets up the instant messaging client as a WordPress widget.
Short URL allows you to create shorter URL’s and keep track of how many times a link has been clicked. It’s useful for managing downloads, keeping track of outbound links and for masking affiliate URL’s.
Smiley JS Buttons allows you to display all the smilies in the default WP set as images next to your comment field. When you click on one of them it appends the code needed to produce that smiley to the comment field.
WP Admin Switcher will show you a drop down on top of all pages and let you switch between blogs. When you switch the plugin will attempt to show the same page of the other blogs administration panel. Requires CURL to be installed along with PHP.