People who use GeoCommons also use:
in 13 toolboxes
Free, Open dynamic web mapper. (An alternative to Google/Yahoo Maps)
in 21 toolboxes
OpenStreetMap is a project aimed squarely at creating and providing free geographic data such as street maps to anyone who wants them.
in 7 toolboxes
Free/Open Source ActiveX GIS Mapping and analysis tool
in 4 toolboxes
Mapufacture provides dynamic, customizable geographic information and collaborative mapping.