I'm hoping to compile a list of add-ins & resources for ArcGIS Explorer. I intend to install it at home, and apparently, there are a number of server feeds out there that can significantly augment the capabilities of this free ESRI software (IMS/WMS servers, toolbox items, etc, etc).
I thought many of you might be interested in having access to such a compilation as well, especially since it's a free software. I'm quite anxious to see what's out there!!
Try your best to give at least a brief description of the add-in/server feed you post in your answers.