I've done this for my club rivers, using google maps. The satalite view is pretty good, rather than map view. You can also add pushpins with photos of where to park, etc.
With google maps you can then publish to the on-line community, and have named collaborators who are the only people who can edit the maps. Perhaps seek regional volunteers off this forum to act as the collaborator for each area.
Here's an example.
http://maps.google.com/maps/ms?ie=UT...d39f9766701745
Best viewed by switching to satalite view, dragging the map and then zooming in. I've added photo's to some of the parking and pushpin signs, kindly taken by the guys from Corwen and District AC. Also take a look at the club's new website 'cos Phil (graylinghunter) has been doing something similar with their fishing maps.
Kev