CREATING PATHS IN GOOGLE EARTH AND USING IT IN GPS DEVICE
(not really related to OpenStreetMap map making)
 
-click on add path in GE
-draw a path (left click to add node, right click to delete. or del key. move with arrows.)
-when finished enter name, description, color.
-right click on it in "places", "save place as", enter name, "save as type"=kml
 
IGO8:
-use gpsbabelgui to convert "Google Earth (Keyhole) Markup Language (.kml)" to igo8.trk.
-copy it to \SDMMC\iGO8\save\TRACKS or just \SDMMC\
-start igo
-in igo: manage/track logs
-click on your track. select color. 
-go back to map
-click on 2d view to view it (2d grid in upper right corner)
 
 
GARMIN:
-use gpsbabelgui to convert "Google Earth (Keyhole) Markup Language (.kml)" to GPX XML (.gpx)
-use mapsource, file open gpx file, "send to device", to send it to garmin device. 
 
 
You can create bat file for converting files. Save content between two --- lines
as "nmea_kml-gpx.bat"
Put it in gps babel dir. Drag and drop file on it.
 
This one will convert 1 file in kml format to igo:
 
---
cd %~dp0
gpsbabel.exe -p "" -w -i kml -f %1 -o igo8 -F %1.trk
pause
---
 
This one will convert 1 file in kml format to gpx for garmin:
 
---
cd %~dp0
gpsbabel.exe -p "" -w -i kml -f %1 -o gpx -F %1.gpx
pause
---
 
 
 
You can use OpenStreetMapLayer.kmz from http://www.markus-bader.de/?p=14 to view osm data in google earth.
Double click on kmz file.