Electric foam rc airplanes are becoming more popular as first-time models simply because they are very robust and lightweight, and can handle rougher landings that are all part of learning to fly radio control.
The Multiplex range - which includes gliders, powered gliders, single motor and multi motor models - are very popular.
The ELAPOR foam used to manufacture these airplanes is not just durable but also very lightweight which gives the model very good flight performance.

If damage does occur, the foam can be easily and quickly repaired with glue or tape which means that on-the-field repairs can be carried out so as not to ruin your flying day. Be careful if using glue though, test it first to make sure that it's not one that dissolves the foam!
Foam planes aren't limited to Multiplex of course, many other manufacturers are using different types of foam or foam-based materials in Ready To Fly rc airplanes. Of course, foam core wings have been used in gas rc airplane kits for years, where the solid foam aerfoil core is covered in a very thin wooden veneer, resulting in a tough and lightweight wing.
But it's only in recent years that whole airplanes have been produced from foam, such as the Multiplex models.
EPP foam (Expanded Polypropylene Particle foam) is another kind of foam often used in the manufacture of RTF planes, particularly in the 'Combat' style slope gliders available from, for example, Canterbury Sailplanes of New Zealand. EPP is extremely resilient and lightweight, ideal for combat slope soaring where mid-air collisions are all part of the action!
A few examples from the range of Multiplex models can be seen below, they are of complete foam construction...
Magister - a high wing foam trainer. This is the RTF package - everything included to get you airborne faster.

Easy Electric Glider - Multiplex have added an electric motor to their popular foam 'Easy Glider', making it an ideal model for some relaxing park flying without the worries of launching a normal glider.

Twin Star II - a high wing, twin motor semi-scale 'passenger' style airplane, looking very realistic in the air and a good introduction to twin motor flying.

Space Scooter - sleek looking mid-wing Park Flyer with a semi-symmetrical wing section for good aerobatic performance. Aileron and elevator control make this a very smooth flyer.
These foam rc airplanes are available from RC Discounts, along with the rest of the Multiplex range.