There's a whole lot of good stuff in Windows Live. adCentre, Search, Messenger, Single Signon (LiveID, formerly known as Passport), Spaces, Virtual Earth, Expo, Writer and a whole bunch of other technologies appearing weekly

And the great thing for developers is that they're not just "Microsoft Only" technologies... they all have open APIs for you to play with.

You can include functionality in your applications, you can extend functionality, you can integrate with one or more existing services, you can mash them up with other services from just about anywhere.

"How?", you ask. Well, the best place to start is with your imagination, an overview, and the SDKs....