The following is written for folks who know nothing or very little about free flight scale modelling.
 
Free flight scale is a challenging (arguably the most challenging) aeromodelling art form dedicated to the construction of free flight (which means no radio control) models of full scale aircraft, either built, planned or conceived. The first goal for a FF scale model is to produce a miniature replica of the full sized aircraft that captures the spirit of that aircraft. The second goal is that the model will fly in a stable predictable manner such that it returns to earth safe and sound and ready for its next adventure.
There are three types of FF scale model: power, where an internal combustion engine or electric or CO2 motor is used to provide motive power; rubber, where lubricated, high-quality rubber strip is used, and rocket power where medium to low powered solid fuel rocket motors (not the ones used for model rockets) provide motive force.
At this point in time the technology exists such that almost any aircraft subject can be built for one of the listed power formats and successfully flown as a free flight model (provided of coarse that the model is of light and accurate construction).
 
So, why fly free flight scale when you have the option of radio control?  I suppose every FF scaler has a different reason but for me it comes down to the elegance of free flight.  A well trimmed free flight scale model circling above with the light shining through the tissue on its wings, is the very picture of elegance. My other reason is that in general flying free flight scale is exceptionally challenging. Every flight requires your full concentration in the preparation process and the flight itself is thrilling from beginning to end. I suppose it is the unpredictability that makes it all very exciting....First just getting a free flight scale model trimmed to fly in a predictable manner is a great and most satisfying endeavor then when you have your ship all trimmed out and flying well you never know if your little handmade bird is going to catch a thermal and clock a two minute flight (an eternity in free flight scale rubber) or if it is going to get caught by a strong gust and tumbled to the ground.  Every flight is thrilling, beautiful, nerve wracking, and wonderful. I have tried just about every aspect of aeromodelling at one point or another and I cannot recommend any other discipline over free flight scale; it is, in my opinion, the pinnacle of our hobby.
 
If you have gotten this far I suppose you are ready to learn a little more about FF scale.
The FF scale discipline is divided into several sub-disciplines (this division is mainly for the sake of competition so that similar formats compete against one another). The main divisions are power scale which includes models driven by electric and CO2 motors and small methanol or diesel engines. Rubber scale which has several categories based on scale and wingspan is the most popular class with rabid enthusiasts the world over. Rocket powered scale models (usually of turbine or jet powered aircraft) has gained popularity over the last few years and is now developing into a standard class in competitions in the U.S. and the United Kingdom.  If you want to learn more about building and flying scale models or if you are just looking for inspiration I strongly recommend that you go through Mike Stuart’s web page which is full of great articles, plans, and pictures. This site is the best dedicate free flight scale site out there right now. Another excellent source of tips, information, inspiration, and advice is the Small Flying Arts (SFA) web site. For plans see the plans page , Dave Livesay’s site, SFA, and FACE plans.