Someone recommended I look for Foxfire #3. We had it in our school library and there was a pretty good series of articles in there on banjo making. The two best things I found there were a drawing of a banjo with measurements and some sketches and a photo of "The Sweeney Banjo." With that information and by scaling a photo of a banjo I liked that had a 12" diameter head and using dividers to figure other measurements I made a full sized drawing of the banjo I wanted to build.
I visited Gagnon's, a local sawmill, and Kenny Gagnon was able to fix me up with "a nice piece of ash" (heehee.) When I got there they were sawing out ashwood and I found a nice clear board. Since it was fresh cut I figured it would be more flexible to bend into the hoop than something that was dried. There was enough wood there for a couple dozen hoops. Maybe I'll make a period tambourine some time or snowshoes with the extra wood. Another possibility is that my sons have expressed an interest in making traditional wooden bows.
For the neck I wanted a piece of poplar (or as they say here in Vermont - "popple") that was 6 inches wide x a little over 2 inches thick. I couldn't find anything at Gagnon's but I found a really nice piece of 2 year-old kiln dried poplar at Johnson Sawmill in Bristol.
I wasn't ready to start trapping and skinning neighbors' cats for the head (as recommended by one of the traditional banjo makers in Foxfire) but I found a maker of African drums, Yendor, who also sold drum supplies and bought a goatskin from him. Rather than carve out the tuning pegs I decided to cheat and buy violin pegs from a local music store. Now I was ready to start cutting and shaping wood ...
UPDATE: Since I first created this website Yendor was no longer able to sell the goatskins over international borders due to restrictions related to mad-cow disease. I now buy my banjo heads from Elderly Instruments. Elderly music also sells many great early banjo instructional tutors - both copies of original tutors and updated tutors in tab.