MapMyRide
GPSies.com
BikeRouteToaster
RidewithGPS
Bikely

Are a few websites on which you can create rides and download them to your device. Lately I use mainly MMR and BRT. You can choose among several sources of map data with these. If you there are decent routable open street maps for your area, you can download these into Garmin Mapsource and create rides there. See: http://garmin.na1400.info/routable.php

For better and more complete responses, try the official Garmin users' forums: https://forums.garmin.com/forumdisplay.php?f=245