Google Earth Outreach provides a platform for non-profits and public benefit organizations, helping them give geographic content to their stories. This site includes a Showcase of different topics, Community resources for organizations, and a number of excellent Tutorials.
ESRI's EdCommunity website features many resources, including ArcLessons, SpatialLABS, Mapping Our World and Case Studies of how GIS is used in a number of fields. You should also visit the GIS Educational Community at ArcGISOnline.
ESRI also assisted the the State of Virginia in creating Historical GIS Projects - Using GIS to Teach History which are ten lessons, complete with downloadable data, to help students learn aspects of US history by using GIS.
In Time and Place "is a growing library of teaching materials for classroom, distance, or home use focusing on selected topics in American history. You will find many traditional reading, map, and photo related resources, but you will also find GIS (Geographic Information System) data and activities as well."
Teach GIS is a new online community and resource for educators, "because no one should face GIS alone."
Hamilton's own Barb Tewksbury presented a seminar on teaching GIS and Remote Sensing in 2010 at the On the Cutting Edge workshop. Although this program focuses on teaching geoscience, there are a number of tips and resources on teaching with GIS in general, including a list of ideal student outcomes.
The Learning Network blog at The New York Times provides suggestions on how to teach various topics, including Ten Ways to Teach About Geography. There were also map-related topics in the Year-End Round-Up 2011 and the Year-End Round-Up 2010.
Jeremy Donald and Mike Winiski of Furman University have put together a blended learning module on data classification to "show you how to understand and use classification when both interpreting and creating maps." They include video tutorials, sample exercises, and a sample curriculum for this kind of work.
The ESRI Spatial Roundtable for February featured a discussion on GIS in Education with contributions from dozens of educators.
The Duke University Teaching and Learning with Google Earth blog features lesson plans, articles, layers and more.