World Wide Instant Messenger
This program lets you run a customizable instant messaging system on your website. All colors, images, text can be modified right down to the menus and installer. It also supports AIM and MSN protocols as well. It comes with 10 different server options. The servers can run on anything from Windows to Unix to Mac. It can also optionally use MySQL. The two clients run on Windows platforms supporting either .NET with redistributable J# or the standard MS JVM that comes with windows.