The Google Map below shows just some of the places that XDS is being used today. This map is a work in progress. I'm still recieving requests from people who want to update it (if you want to become a collaborator, e-mail me).
The map currently shows those institutions where an XDS infrastructure is being used to connect provider organizations to other healthcare providers. It does not yet show the geographic regions covered by these implementations (except in one case). Some of these HIEs cover areas as small as a single community and others an entire state, region or even whole country. This map doesn't cover every XDS implementation in the world, only the ones that I and others have knowledge of.
View Where in the World is XDS/XCA in a larger map
This map originated in a presentation given four years ago at an IHE event, and has since become one of the most reused slides in IHE until now. I hope the Google Map takes its place going forward. You can see how the map has morphed through the hands of several presenters with access to different and more recent information below. The slides just highlight some of the more well known XDS implementation in the world, they don't cover all of them. There are a large number of places where providers don't even know that XDS is in use, which is exactly as it should be, and which sometimes makes it difficult to track.
The next time someone asks the question, "Where is XDS used?", feel free to point them to this map. If they happen to be from the US, you might also point them to two webinars HITSP gave on this topic over the past year. The first discusses real world HIE sites that are using the HITSP specifications in production today. The other describes the work of the NHIN implementation projects which also use XDS (and appears on the May 2008 slide above).