There are two kinds of polaroid transfer, both about equally rewarding:
The first it dye transfer, which has already been covered.
The second is emulsion transfer, which is a lot more predictable:
To do this, you boil (almost literally) the emulsion off a normally developed polaroid image, then transfer the emulsion (carefully!) to the substrate of your choise.
Example enclosed - polaroid emulsion on watercolour paper: Moved to HERE