Joseph Elfelt of MappingSupport.com has posted a new PDF file containing URLs for local, state, and federal ArcGIS Servers with open data. Here is the updated list:
The primary purpose of this list is to provide the REST service endpoints for government servers with open data. All of these links end in “rest/services”. In particular, Joseph hopes that students in middle school and high school will eventually use this list to explore geospatial data for their local communities.
And of course the list is not complete. So if you know of additional government ArcGIS servers with open data, please send Joseph the REST service endpoint and he will update the list.