Are you looking to develop plugin's that you can attach to these messangers. If yes Check the below links, on which platform these are developed should not matter. finally you just have the executable. http://developer.yahoo.com/messenger/[^] http://dev.aol.com/aim/plugins[^] http://channel9.msdn.com/forums/TechOff/101812-MSN-Messenger-Development/[^] http://forum.skype.com/index.php?s=606f036c3cec316698882051231177d0&showforum=16[^] http://code.google.com/apis/apps/[^]