I use RedPine mapping trailmaps on my Garmin NUVI 500. Used them for several years now. Routable, plus I also use gamins mapsource software on my laptop to map out routes the night before so we know where we're going and how far it is.
Ya, I'd still like to figure that mapsource out a bit more. I forget what program I'm using now, but all the trails are there which is nice, and it was a free download. I think the redpine costs money if I'm not mistaken....