MAPC2MAPC Help pages Online Map sources
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Here are some sources of maps and how to process them with MAPC2MAPC
This is not an exhaustive list : please Email me to suggest additions
Try MAPPUZZLE to download from some on-line servers.
Kystinfo Norway marine chartsSupported from version 563 - open the zip archive.
Morocco MapsCalibrate using the Latitudes/longitudes and Merchich Datum then use Edit>Fit Coordinates, Other Grid, EPSG26191 (north) or EPSG26192 (south)
Russian mapsJPG images that require calibration.
Various Russian maps and some US army. Loadmap.netOZI MAPfiles with GIF images : open the MAP file
Pacific Marine CartsDownload as zip file and open the KAP file(s) you need. Needs MAPC2MAPC version 552 or later for the charts that span 180 degrees.
Nepal topo mapsDownload as JPG, need to calibrate using Nepal Grid
Brazil marine chartsDownload as KAP. Includes part of Antarctica such as South Shetland Islands and major rivers including the Amazon..
Canada TopoDownload as GEOTIF
USGS Topo
May not work with Firefox
Download as GEOPDF
Upper Mississipi River ChartsDownload as GEOPDF. Some of these cannot be processed by GDAL so install Foxit Advanced PDF Editor, load the PDF and save them without changing.
Netherlands Marine ChartsOpen the WCI files directly in MAPC2MAPC versions 533 and after
Finland Various scales with a very flexible licence. Download as TIF+TAB : open the TAB file.
elrincondelmapa.comSpain, France and Portugal.  ECW files can be processed either as a single map "Open Via GDAL" if small enough or using Utilities>Convert Huge Map to Mobile Atlas. From version 532 (~1 June 2014) MAPC2MAPC will read these RMAP files so will process the France and Spain maps.
MAPSTORmapstor.com offers unique access to a large number of digital images of topographic maps at a scale of 1:1000 000 to 1:50 000. These maps were created by agencies in Russia and other East European countries for military purposes during the Cold War era in the late 20th century. Maps are supplied as GIF image with MAP calibration. Open the MAP
Erstwhile YugoslaviaDownload as GEOTIFF. Use File>Open Calibrated map and select GEOTIF.
To remove the collars, check 'Crop KAP and PDF when loading' in Settings Load tab.
Discovery Walking Guides'Tour and Trail' maps of Canary Islands, Mallorca, Minorca, Madeira and selected areas of Southern Spain. 

Use File>Open Calibrated Map to open the KMZ file
Denmark
Netherlands TOP25
Download the zip file; unzip it and copy the TIF file to another folder.
Use File>Open Calibrated Map and select GEOTIF as the file type to open the TIF
[Use version 524 or later]
Ordnance Survey Opendata
Miniscale, District Raster, 1:250000 and Streetview
Copy the TAB file to the same folder as the TIF image that you want.
Use File>Open Calibrated Map and select Mapinfo as the file type
Spain IGN maps MTN50 and MTN25 raster
For each sheet, download the .TIF, .PRJ and  .TFW files and place them all in the same folder.
Use File>Open Calibrated Map and open the TFW (world file). Match ETRS89 datum with EUREF89
US Nautical Charts
Download the ZIP file; unzip it and copy the KAP file(s) to a folder.
Use File>Open Calibrated Map and select BSB Charts as the file type. You may want to set automatic crop in Edit>Preferences Load tab
US Aeronautical Charts
Dowload the zip file; unzip it and copy the TIF file to another folder.
Use File>Open Calibrated Map and select GEOTIF as the file type to open the TIF
Australia Mapconnect
Download as GEOPDF files. Unzip the download and copy to a folder.
Use File>Open Calibrated Map and select GEOPDF as the file type.
New Zealind Linz Topo
Download as GEOTIFF. Use File>Open Calibrated map and select GEOTIF. (The TIFF files are smaller but have no calibration information).
Note about GEOPDF files : GDAL will sometimes fail with a message about corrupt PDF or attempting to rebuild XREF table. Try downloading Foxit PDF editor. Then load the PDF file in Foxit and save it without making any changes. This can be done without payment for Foxit.