Alvaro Luna Bautista has worked for more than four months on a model of a Policarpov I-15 Chato aircraft. During this period he has documented his efforts step by step. The result is an incredibly detailed tutorial with many screenshots, reference images and downloadable files.
This one is not for absolute Blender newbies or for the faint of heart, but if I had a rating system for tutorials, I'd give this one five stars!
You'll find it on the CGSociety forum.