Martin Parry (MS UK Evangelist) wrote a killer article on Windows Live Data. The area he focused on was the Contacts API.

In Hotmail/Messenger/Spaces the address book has been unified. Now we have such a rich address book(s) (500 million) with lots of contacts (and 30 billion relationships) that data wants to be free.

Basically the way it works is:

  • a webmaster can request permissions (read or read/write) from a user to access their contacts.

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  • once the permissions are granted by the user they get back a token which is used to access the contacts REST API.
  • Contacts come back as XML and you can READ/ADD/UPDATE/DELETE (GET/POST/PUT/DELETE).

To see the working and to dig deeper see www.randomthirdparty.com (dev's shouldn't name domains). This is a public website which is similar to an interactive SDK

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Check out Martin's article or the SDK or an implementation for Contoso University or cruise over to dev.live.com to see what other services there are.