Samir from the Windows Live Expo team has posted an entry entitled Attention Developers: Expo API RTW where he writes

The first version of the Expo API went live this week.  The API gives developers read access to the Expo classifieds listings database.  All our listings are geo-tagged, so there are some cool posibilities for mashups with some of those mapping APIs.
The API docs are published on MSDN and you can find them here.  You can get started by signing up for an Application key at
If you've got a slick working demo using our APIs, please let us know at so we can link to it.  The nuttier and more creative, the better!  Also, make sure you post a link from this blog post.

I took a gander at the API before I shipped and there are a number of things I like about it. The first thing I like is that the API has both a RESTful interface and a SOAP interface. Even better is that the RESTful interface is powered by RSS with a couple of extensions thrown in. This API and others like it that we have planned is one of the reasons I've been thinking about Best Practices for Extending RSS and Atom. On the other hand, I don't like that the API takes latitude/longitudes instead of addresses and zip codes. This means if I want to write an app that uses the Expo API, I need to also use a geocoding API. This may make it easier to integrate Windows Live Expo into Map-based mashups though. I've asked Samir about also accepting addresses and zip code support in the API but I suspect the team will need to get the request from a couple more folks before they take it seriously. :(

I've promised the Expo folks that I'll write a gadget using the API which I hope to get started on soon. Given that I've also promised the folks at O'Reilly's an article on building gadgets by next week, I better get cracking. It's a good thing I have a copious amount of free time. ;)