What can you do with Windows Live Messenger?

Windows Live Messenger has a potential audience of 240 million users. This means great opportunities for both businesses (free API access, ad servers, pay-for-placement,) as well as hobbyists (interactive multi-user apps, DHTML and AJAX development.) With Internet Explorer now directly accessable in Windows Live Messenger, the aim is to create a user experience that is all about interactivity and engagement.