This site shows a bunch of different models:
http://www.angelfire.com/space/proto57/rdf.html
Not that I need to collect anything else, but some are quite cool.
I remember as a kid, building a Heathkit DF-1 for a friend of my parents that had a boat. It seemed at the time that it was a pretty decent radio, but I suspect that I would not think that today.
jr