The following programs are provided with no guarentee or endorsement by the USGS. 
See company web sites for support and futher information


ArcGISPluginWithCompressorV2.0_RC1.exe	plugin to ARC8.3 and higher for ERMAPPER format grids 
						(ecw,alg,and others)
geosoft_arcplugin_setup.zip  		plugin to ARC8.3 and higher for GEOSOFT Oasis format grids
						(grd and others) BETA version
Oasis montaj Viewer 6.0.1.exe  		free viewer for grids and maps from generated in Oasis
					can convert Geosoft grid files and data bases