Got my Google Co-op feed working
After reading through the developer guide, I was able to quickly crank out a test XML file to create Subscription Links in Google Co-op. Here is my Google Co-op profile page where you can preview and/or sign up for a sMoRTy71 subscription.

Basically, the test XML file looks for the query "sMoRTy71" and then serves up a link and description to my site in the results. Not rocket science, but still cool to see working.

Here is a screenshot of the results:

The green area is where subscription link results are displayed

Now that I've got it working, I've gotten to figure out what the hell I can do with it.

BTW, if you want to see my super simple XML test file, check it out here.