Hello Adam,
Not sure what you're looking for exactly, but start with reading the entry and judging criteria located here is a good place to start: http://imaginecup.com/Competition/InteroperabilityAward.aspx It also has links to how to submit your entry, if that is the part that is causing confusion.
Craig talks about interoperability on his blog at http://blogs.msdn.com/craig.
Craig also chats in this video about what is interoperability and the contest itself http://channel8.msdn.com/Posts/Imagine-Cup-and-the-Interoperability-Challenge-There-are-now-more-reasons-to-compete/
Since we know that interoperability is complex we've also posted 2 additional Channel 8 videos to help get you started:
This one discussed Interoperability judging criteria and the future of user-centric identity and how interoperability can help pull together existing environmental related technologies. To see the video go here: http://channel8.msdn.com/Posts/More-about-the-Interoperability-and-the-Interop-Challenge-for-Imagine-Cup-2008/
This one is talking about Web Services, even some tips for both using and creating Web Services:
http://channel8.msdn.com/Posts/Interoperability-Challenge-Web-services-and-prizes-for-Imagine-Cup/
If you still have more specific questions after reviewing these please let me know & I'll get you answers.
Hope to see your entry for our Award,