By snap-together I'll assume you mean plastic models, in which case I can't help you there as my first model was a glue together B-52 and I never looked back. I'm sure there are plenty of generic modeling resources that can apply to both plastic and wood so I will just focus on books/resources that I am aware of that pertain to wooden models.
Don Ross's Books are great for free flight on rubber power and sort of useful for other power sources and controlled flight. A lot in the R/C world has changed in recent years which really out dates that part of his two books.
Mike's flying scale model pages are a great online resource for free flight, especially rubber powered.
I would be remiss to not also mention the
Virtual Aerodrome as a great resource to see how others build their planes and to ask questions on their techniques.
Good forums are
Small Flying Arts for all things flying related and
RCGroups for all things R/C related.