The first link: http://www.wisdomking.com/product/aquaplast-t-18 is used in the medical industry for splinting. It comes in sheets and when soaked in hot water can be bent to the desired shape. Sheets can also be easily cut into the desired shape.
The next product, shapelock, comes in small moldable beads. You can heat these in water or with a heat gun. The resultant piece can be machined and painted. I have some of this in multiple colors, and it really is a fun thing to play around with. I think it would be great for prototypes, and special props, as well as specialty connectors. I wouldn't use it in critical situations, but the finished piece is as solid as you can expect a piece of plastic to be.
The link to the shapelock is here: http://shapelock.com/index.html