My twitter app uses a web service hosted on my site to get all the necessary Xbox Live info…. way more than the twitter app actually uses. This is a SOAP API, located here:

http://duncanmackenzie.net/services/XboxInfo.asmx

I know that some people prefer a more RESTful API though, so I also have another ‘page’ that you can call with a straight GET request and just pass the gamertag in as a query string parameter:

http://duncanmackenzie.net/services/GetXboxInfo.aspx?GamerTag=Festive+Turkey

Enjoy!