There is a great article in this months issue of Wooden Boat Magazine that lists most of the well known wooden boat kit providers. It covers from small to large and all types. Of the builders on this forum, Tatman Wooden Boats, Ray's River Dories, and Montana Boatbuilders all are listed for river dories.
I'll find a link and also see if I can get permission to re-print the article.
HERE is the link to the the Wooden Boat website and the table of contents of the current issue. On page 54 is an article called "the sum of its parts" which outlines the advantages and savings of purchasing a kit vs. going it alone. It also lists many wooden boat kit makers for all kinds of boats. It 's a great resource.
I'm going to try to get permission to reprint this article on this site after the on shelf issue has expired. I'm sure this question will be coming up often.