The Grassroots Mapping wiki collects information, how-tos, current projects and general resources for creating your own georectified aerial imagery using cheap hardware to acquire the imagery (balloons, kites, and UAVs). Check out the main site for blog entries on current projects as well. From the website:
Seeking to invert the traditional power structure of cartography, the grassroots mappers used helium balloons and kites to loft their own “community satellites” made with inexpensive digital cameras. The resulting images, which are owned by the residents, are georeferenced and stitched into maps which are 100x higher resolution that those offered by Google, at extremely low cost. In some cases these maps may be used to support residents’ claims to land title. By creating open-source tools to include everyday people in exploring and defining their own geography, Warren hopes to enable a diverse set of alternative agendas and practices, and to emphasize the fundamentally narrative and subjective aspects of mapping over its use as a medium of control.
One of the resources highlighted is the Cartagen Knitter, a simple online application for knitting together multiple aerial images into a single one for georeferencing using GIS software or an online service like Map Warper. Here’s a video demo:
More related videos here.