Get started with OpenSocial. Orkut, Hi5 and MySpace support it. Its just plain javascript and easy. So start here. Ofcourse, you will need small tweaks when run

Get started with OpenSocial. Orkut, Hi5 and MySpace support it. Its just plain javascript and easy. So start here. Ofcourse, you will need small tweaks when running your app on different containers. Containers in simpler words mean sites. Then do it for Facebook. Then your app will also run on Bebo with very little tweaks.