National Agriculture Imagery Program
Through the National Agriculture Imagery Program (NAIP), the US Department of Agriculture's Farm Service Agency acquires 1-meter aerial imagery covering the United States. The "leaf on" imagery is collected during agriculture growing seasons. It is frequently newer than other easily-available imagery (Yahoo, Bing) and can therefore be used for mapping recent changes.
In some areas (at least parts of Texas) Bing serves NAIP imagery.
For the JOSM WMS Plugin, the possible WMS url are
http://isse.cr.usgs.gov/ArcGIS/services/Combined/SDDS_Imagery/MapServer/WMSServer?request=getmap&version=1.1.1&format=image/png&srs=EPSG:4326&layers=0&styles=default& http://isse.cr.usgs.gov/ArcGIS/services/Combined/USGS_EDC_Ortho_NAIP/MapServer/WMSServer?request=getmap&version=1.1.1&format=image/png&srs=EPSG:4326&layers=0&styles=default& http://isse.cr.usgs.gov/ArcGIS/services/Combined/USGS_EDC_Ortho_NAIP/MapServer/WMSServer?request=GetMap&version=1.1.0&format=image/jpeg&service=WMS&layers=0&STYLES=default&
2010 imagery was added in May 2011.
NAIP can also be accessed directly from the USDA's WMS; however, there are multiple services (one per state, excluding Alaska and Hawaii). Each state's link is listed at http://gis.apfo.usda.gov/arcgis/rest/services/NAIP; the link can then be used to add the layer in JOSM's WMS preferences. More detailed instructions from Simon Legner are here.
A JOSM-format URL:
As of May 2011, final 2010 imagery is available and is also accessible via:
This is not always the latest imagery (example: the official NAIP server and MapQuest show more progress than Telascience on the US 54 expressway at Osage Beach, Missouri).
The USDA's Geospatial Data Gateway makes available downloadable county-wide image mosaics of NAIP imagery, other DOQs, DRGs, etc. Unfortunately, they are distributed in proprietary formats (MrSID, JPEG2000) and will require involved conversion before use in most software.