by Nick Bosch on WordPress.org
WP Dashboard Chat is a Twitter inspired widget, which displays on the admin dashboard. It allows for quick communication between users and admins.

The chat interface.
WP Dashboard Chat allows admins to communicate via a widget which displays on the Admin Dashboard. It’s perfect for quickly getting messages out to all your sites writers or having a formal meeting. Features include, @ mentions and replies, live updating, Gravatar support, auto-linking and HTML formatting. Many more coming soon!