Making your presence known
Ever wanted to make your online presence known and allow people to send you an IM without having to install an IM client or adding you to their buddy lists?
Sure. Here we go. Microsoft has made an IM control and API available for such use.
You can find the necessary details on http://blogs.msdn.com/angus_logan/archive/2007/11/07/announcment-windows-live-messenger-im-control-presence-api-conversations-from-web-to-client-querying-presence.aspx