UPDATE: The code for this post is available at the bottom of the page.
I have been doing a lot of development with the ESRI Silverlight API recently. One of the requirements of my project is to be able to dynamically add KML data at runtime. The incorporation of KML was handled for us through one of the ESRI samples on the resource center so we pretty much just had to integrate that code and test against our use cases. For testing, I typically reached out to GeoCommons since any data set available there can be streamed as KML.
Obviously, this is not my first exposure to GeoCommons but, when discussing it, I found that many of the analysts I spoke with were not aware of it and did not use it much. So I decided to tackle developing a simple ArcMap extension to allow a user to search GeoCommons and then download/add data to ArcMap without the need to manually download, unzip and add the data themselves.