I use www.bikeroutetoaster.com to do "turn-by-turn" navigation on the Garmin Edge 305. The designer of that particular site decided to add Course Points at the turns when you draw the map, and you can edit them on the cue sheet page. I put the road name in the Course Point Name (up to 10 characters). Then I download TCX file to the Edge 305 and Select Training --> Courses on the Edge. "Do Course".

On the Course page, you'll see a field called "Dist to Crs" or something like that. It will display the distance to the next course point, the direction of the next point, and your course point name. The map will display the directional symbols of the turns on the "breadcrumb" trail.

Works pretty good as a "fudge" for Turn-by-Turn. The problem is that Course Points take up a lot of memory, so you'll have to load these one or two courses at a time. I don't use his Course Point warnings feature, which adds a second course point 200ft or so before the turn to warn you, just because it takes up too much memory.

Anyway, not perfect, but I've been surviving that way for 2 years now.