Free map images can be downloaded from these sites.
Note: For unregistered users: You will need to use the Trial version to use these maps, the unregistered Shareware Demo version cannot be used with these images. (The Trial version is included in the OziExplorer Software download.) These maps will require importing into OziExplorer using the Import Maps option on the File menu, then use the Import DRG ..... menu option.
Libre Map Project
24k scale USGS DRG's - detailed topographic maps for all 50 states of the USA in tif and/or geotiff format - suitable for use with OziExplorer.
Digital Data Services
24k scale USGS DRG's - detailed topographic maps for all of the USA in geotiff format - suitable for use with OziExplorer.
This site was free but now there does not appear to be any free maps.
USDA Geospatial Data Gateway
CAUTION - This site delivers maps in GeoPDF format which are not suitable for use in OziExplorer.
The Geospatial Data Gateway or Geo-Data Gateway provides access to natural resource data. You can search for available data by geographic area such as county or state, use the point and click map tool to find your area of interest; using a gazetteer, or by entering latitude and longitude coordinates. (Note: See the FAQ on the Data Gateway website if the map does not show in your browser)
Click on the "Get Data" link on the top of the Geospatial Data gateway page to show the USA map to locate an area.
Nautical Charts - NOAA Raster Navigational Charts (NOAA RNCs™) are distributed here. These RNC charts are raster images which can be imported into OziExplorer using the Import Maps / BSB Chart option. (These are not ENC charts but appear to cover the same regions.)
Maps in TIFF format 1:24K, 1:100K and 1:250K. Not all downloads are free. Maps can be purchased on CD for only a few dollars.
University of Texas Library Online
Free maps and listing of other maps available.
Doyle's Links Page (Links to map sites)
Custom High Resolution Lake Mapping ; 3D Lake Terrain Imaging
TopoFactory - Create custom topographic maps
GPS Trails - Alaskan USGS maps on CD and Alaskan GPS trail data
DRG's for All States