As Kip mentioned earlier, we're expecting a major Windows Live platform announcement to be made at Mix '06 later today. As Steve Ballmer said back in September 2005, Microsoft wants to "Win the web" and to do this they are looking to provide new ways for independent developers to build on Windows Live services. This can either be to improve user experiences by integrating with user data such as Windows Live Contacts and online presence or to achieve better business results via AdCenter and the as yet unreleased billing and micropayment system. In both cases, Microsoft is looking to expose its massive-scale services as a rich developer platform, to be made available to "hobbyists" as well as large ISVs.
In order to do this effectively, the new Windows Live DevCenter will be act as a complete developer portal, allowing developers to register, manage, and track their applications as well as learn about the Windows Live platform from Microsoft and from other developers in the community. As Dare mentions, this new group will attempt to support and suplement the Windows Live platform of services. Already Imran has asked for suggestions about how Windows Live Mail could be extended, and I suspect this is only the beginning.
As Kip pointed out, it still remains to be seen exactly how open Windows Live will actually become and how data security will be maintained. Perhaps the real question is will access to the developer platform be only available via gadgets as Brandon has suggested? These haven't really taken off yet, however Microsoft has put a large emphasis on their importance by including gadget support in Windows Vista.
One thing is for sure though, there is going to be a lot of talk about this after the announcement today. Here's hoping the session is broadcast live online.