also: Shapelock, Polycaprolactone, Friendly Plastic, InstaMorph
Polymorph is an low temperature thermoplastic. Super strong and tough. It melts at around 65 degrees Celsius and hardens at room temperature. It comes as small white pellets that go transparent when put in hot water. They can then be formed and become opaque again as they cool off.

Liquid Polymorph

An unusual plastic that is liquid at room temperature but solidifies at 2 degrees Celsius.

Suppliers

Nice summary >> http://reprap.org/bin/view/Main/Polymorph
>> http://shapelock.com/ (USA)
>> http://www.mutr.co.uk/product_info.php?products_id=551 (UK)
>> http://www.instamorph.com/ (USA)