What sort of patents are have been granted against 3D printing?

This is an interesting one that was touched on a little recently when exploring why RepRap chose FDM and not another 3D printing technique. What sorts of patents have been granted against 3D printing techniques, and what sort of patent portfolios do the various players in the space have kicking around?

This is a companion discussion topic for the original entry at https://reprage.com/post/47776307526/what-sort-of-patents-are-have-been-granted-against-3d