Ideally you need to provide us with more information: Does your friend have a sat nav, Garmin or otherwise, or does he just need to see your route?
If the latter then I suggest that you download
ITN Converter and, having saved your route from Mapsource or Basecamp, open it in this program. You can then select Google Maps as an export format. This will open your route in Google Maps in your browser. Send him the URL for this and he'll be able to view your route.
Due to slight differences between the Garmin and Google routing algorithms there is a chance that there will be differences in the route, depends on the complexity of your route and the availability of close viable alternatives in the road network between points. If this is the case then open the ITN Converter editor by clicking the 'Editor' button. You can then make changes to the route so as to reflect what you did in Mapsource, exit/close the editor window and these changes will now be incorporated into the route, export to Google Maps again or to the format of your choice.
ITN Converter uses the Google Maps API by default to calculate and draw your route. You can change this to other providers and more interestingly you can also change the map display to the likes of ViaMichelin which, at certain zoom levels, displays the green edges to scenic roads. These, practically without fail, make a great biking roads.