Caleb Kraft of hackaday.com designed Oculus Rift accessory mounts that can be 3D printed on most any 3D printer. This allows you to mount things like webcams and sensors to the Oculus Rift to aid in immersion. You can download the STL files for this from Thingiverse.com.
Caleb describes what inspired him to design these.
While browsing an oculus rift thread on reddit, I saw someone mention how nice it would be to have some actual mounts for external sensors on their Rift. The idea is that adding additional sensors or cameras will allow us to expand the capabilities of the rift. With something like the Razor Hydra, you can add quick positional tracking (the rift only tracks rotation, not position). With some webcams, you could theoretically do some stereoscopic augmented reality.