While you'll find kits for models, and plans for half models in this section, keep in mind for you "scratch" builders, that you can build models from some books.      build a whitehall from the book Building Catherine, by scaling down the measurements given in the book for molds, etc.
build a skiff from the book Heidi (another Rich Kolin book)
build the Joel White Catspaw design from the book How to Build the Catspaw Dinghy
And if you wanted to scratch-build a half model you could learn how from the article in WB 182 (available as a digital download)...
and then use a good book like Small Yachts, to get the lines.