Shoutbox

I haven't used it in forever because it seems to have stopped being developed but if you're still using MSN Messenger, you can use Stuff-Plug Ng http://www.stuffplug.com I'm fairly sure it only works with MSN Messenger 7.5 and below. Stuff Plug 3 will hopefully be released shortly and that will work with Windows Live Messenger only.

Edit// Also, if you're looking for another program that works right now for Windows Live Messenger, I think MessengerDiscovery Live may do the trick for you. I'm not 100% sure about this though.