A new thing I have just found on ubuntu 9.04 which is out in 17 days is the indicator applet. It simply works with pidgin and evolution and tells you whats going on. New emails, friends signing in on pidgin etc. It works very nicely with notify-osd the new notification system in ubuntu.
If you want to find out about notify-osd read mark shuttleworth’s blog
http://www.markshuttleworth.com/archives/253
Also in the video on mark’s blog is the Indicator-applet, its in the place where the deskbar would normally be in ubuntu.
To enable it on ubuntu 9.04 you right click on a panel and select add to panel, look down the list and you will find the Indicator-applet.