OSM maps of USA focusing on Error detection
Ben Konrath's routable OSM map of Martinique
Raumbezug's OSM map of Bulgaria
Cloudmade's OSM maps of Cameroon for OSM improvement
OpenMTBmap of Luxembourg
This is a collection of nice topographic maps from Afghanistan. They feature roads, rivers, settlements, POIs and contour lines. They also provide english transliteration of the names.