A look at modeling a Slinky in Blender from Craig Forster, who shows an interesting technique for building the spiral shape and allowing it to bend into place.
modeling a slinky in blender 2.67 using a nurbs curve and posing the slinky with a path curve
Craig notes that the most obvious workflow would be to add a circle with a screw modifier applied, however, the model will be too large to really be of value with this technique. Craig demonstrates the same practical results by using NURBS curve and posing the Slinky shape with a Curve.