The maps on this site have been obtained using the excellent gmap4 service. To obtain a map, all you need to do is form an URL which asks gmap4 to produce a map using a given GPX file, as in
http://www.mappingsupport.com/p/gmap4.php?q=http://share.jointwork.net/tdr_file_site/tracks/Loch_Leven.GPX&t=t4
The parameter t indicates the type of map (Google Terrain, USGS Topo, etc); I recommend t=t4, which are high-resolution topo maps with shading.
Tahoe Donner Ramblings 