Dunst
Lightweight and customizable notification daemon
...Customize fonts, icons, timeouts, and more. Are you unhappy with the default shortcuts and colors? No worries, you can change these all with a simple configuration file tweak. Change the look or behavior of notifications matching a specified pattern. You could use this to change the color of message notifications from your favorite jabber buddies, or to prevent important work email notifications from disappearing until you manually dismiss them. Specify the monitor that notifications should display on, or have them appear on the monitor with keyboard or mouse focus. ...