I started mapping using my Nokia C5 phone with its GPS capability but I now have a Garmin eTrex Vista HCx.
I get my maps from TalkyToaster. I simply transfer the map file to the Garmin folder on the micro SDHC card.
Mapping cycle routes
I got into OpenStrretMap through cyclestreets.net. This really got me interested and I was spurred on to map my local routes so that they showed up correctly on cyclestreets. In the main, this means that the quietest route used the local cycle routes.