Gnat

Deceptively simple, this model is easy to build and teaches you the basics of trimming. It is also a lot of fun.

The Gnat can be found on the  Project Air website. If you have some balsa and a prop, it can be made directly from the images on the AMA plans  site. The plane is so simple it can be made from this article. 

Don Ross has written an excellent  book  'Rubber Powered Model Airplanes', that includes this model as well as information I still find useful.

Trimming

A freeflight model has to fly by itself, auto-correcting for the forces that disturb its flight. This magic needs a bit of a helping hand to work - we call this trimming.

The Swiss Rubber Twisters

This is a group of model flyers and constructors in Swizerland, who concentrate on  flying rubber-powered planes. They arrange several events a year, detailed on their webpage