Essential Tools from Syncfusion provides you a SplashControl/Panel that
provides you the Messenger style popup UI, among other things.
Take a look at the feature list, download a demo and a free eval:
http://www.syncfusion.com/products/tools.asp
Other then that, if you don't want to spent money, you can just create a borderless window which you animate (move) from behind the taskbar, that is pretty much all it is. have a small window let's say 60x60 and position it ResolutionWidth + 60 and ResolutionHeight + 60; then if the event is fired that you want the window to appear, change the height -60 and width -60 So it will appear it comes from the tray icon. The nifty thing is now, if a user has the taskbar on top or on the side to check that and have the window appear from there. But this should give you a pointer on where to go.