"The Free Wiki World Map." Easily the largest community mapping effort in human history. A dynamic, user contributed world map, with data export and developer API capacities. An excellent resource for GIS data for the developing world.

The Humanitarian OpenStreetMap Team (H.O.T.) ( hot.openstreetmap.org) coordinates the creation, production and distribution of free mapping resources to support humanitarian relief efforts in many places around the world. Launched in January 2009 and incorporated in August 2010 as a US NGO, it aims to apply the principles and activities of open source and open data sharing to humanitarian response and economic development and support the growth of the OpenStreetMap project. Collaborative mapping is uniquely valuable to humanitarian work, especially in places where base map data is often scarce and out of date.

Using inexpensive DIY techniques, PLOTS seeks to change how people see the world in environmental, social, and political terms. They are activists, educators, technologists, and community organizers interested in new ways to promote action, intervention, and awareness through a participatory research model.

This community began as the Grassroots Mapping project, an effort to produce Do-It-Yourself satellite imagery with balloons and kites, most notably during the 2010 BP oil spill. They are now broadening their scope to explore new inexpensive and community-led means to measure and explore environmental and social issues, including Spectrometry, IR & Thermal Photography, etc...

Participatory Avenues aims at sharing significant progress in visualizing community-based knowledge and perceptions and in providing stakeholders and less-favored community members added stake in tailoring and owning development and natural resource management initiatives.

Of particular interest are the simple and lo-tech methods for Participatory 3-Dimensional Modelling, or P3DM (http://iapad.org/participatory_p3dm.htm), which uses easily accessible materials and methods (cardboard contour mapping, paper mache, etc...) for creating large-scale topographic models of communities, by communities.

Field Papers allows you to print a multipage paper atlas of anywhere in the world and take it outside, offline, in the field. You can scribble on it, draw things, make notes. When you upload a snapshot of your print to Field Papers, they'll do some magic on the server to put it back in the right spot on the map. You can transcribe your notes into digital form and share the result with your colleagues or download the notes for later analysis. You don't need a GPS to make a map or learn complicated desktop GIS software to use Field Papers. It's as easy as print, mark, scan.
Field Papers in an open source project hosted at Github - https://github.com/stamen/fieldpapers

Part of the Public Laboratory for Open Technology and Science, founded by a group of activists, educators, technologists, and community organizers interested in new ways to promote action, intervention, and awareness through a participatory research model.

Just a few hours after the 7.0 magnitude earthquake hit Haiti in January 2010 the OpenStreetMap Community began tracing.... What did they begin tracing? Roads in the beginning all from imagery that was previously available from Yahoo. This initial tracing enhanced the base data that was already present. The initial data was from responses to 2008 cyclones Ike Hanna and Gustav that was imported in OSM in Jan 2009. This data served as a starting place for the mapping that would take place after the earthquake.

Within 48 hours high resolution imagery taken post-earthquake became available. Within the first month over 600 people added information to OpenStreetMap in Haiti. It became the default basemap for responding organizations such as Search and Rescue teams, Humanitarian mapping NGOs like MapAction and iMMAP, the United Nations and the World Bank...

The exercise was facilitated in order to train members of the communities of Ulu Papar in the practice and establish a medium (the 3D model) where community members could interact and share location-specific knowledge in an easy way
A second purpose of the exercise was to generate spatial data which could be digitised and used as part of wider effort supporting community-based conservation in Ulu Papar.

Since May 2010, The Public Laboratory for Open Technology and Science (PLOTS) has been using balloon mapping to capture aerial imagery of spill-affected sites in Louisiana, Mississippi, Alabama and Florida. Their work on the Gulf Coast in 2010, was done in cooperation with groups such as the Louisiana Bucket Brigade and the University of South Alabama on a community-led monitoring of the Deepwater Horizon oil spill.

Ubernerd Jeffrey Warren's foundational thesis on Grassroots Mapping.

Abstract:
Geospatial tools and information play an important role in urban planning and policymaking, and maps have diverse uses in legal, environmental, political, land rights, and social arenas. Widespread participation in mapmaking and access to its benefits is limited by obscure and expensive tools and techniques. This has resulted in poor or nonexistent maps for much of the world’s population, especially in areas of urban poverty. In particular, public access to recent and high-resolution satellite imagery is largely controlled by government and large industry. This thesis proposes balloon and kite aerial photography as a low-cost and easy to learn means to collect aerial imagery for mapping, and introduces a novel open-source online tool for orthorectifying and compositing images into maps. More...

Kibera in Nairobi, Kenya, was a blank spot on the map until November 2009, when young Kiberans created the first free and open digital map of their own community. Map Kibera has now grown into a complete interactive community information project.

The Gowanus Canal Conservancy is conducting environmental investigations in the Gowanus Canal sub-watershed by using balloons and kites to capture aerial imagery. They have completed a four-part set of seasonal imagery from 2011, which is hosted in their archive. Sometimes they use a stereo camera rig to collect infrared imagery in addition to visible imagery. The data documents patterns/concentrations of vegetation or possible contaminants, monitors the stormwater retention design interventions that the GCC is installing along the canal edge, and reveals unknown or unidentified pipes or sources of groundwater entering the canal. In the long-term, this inquiry effort seeks to address the 300M gallons of untreated sewage that will continue entering the canal yearly even after the EPA finishes their Superfund clean-up of the toxic sediments at the bottom of the canal.