Remember the PSP? Me neither, but someone does and they've brought you the PPSSPP VR, an emulator for Sony's initial handheld offering that lets you play PSP games on the Oculus Rift DK2 in VR.
PPSSPP VR brings a lot of new elements to the mix with head tracking, stereoscopic 3D and pre-warping, which means rather than just playing PSP games with the equivalent of a PSP strapped to your face you can actually look around the game world at a higher resolution than the original console.
Obviously, in addition to the emulator you'll also need an ISO created from an original PSP game, which you need to legally own before acquiring, so do be sure to own original copies of games you're trying to play on the emulator, you monsters.
This is the first version of the emulator to add VR functionality but it's based on the well-respect PPSSPP emulator, so many of the bugs with the emulation are already ironed out.
Initial tests seem to indicate that my Xbox 360 controller worked fine without any tweaking and most of the menus are usable from within the headset. Game compatibility seems solid and should only improve over time.
You can pick up the emulator from the Oculus forums, but remember you need to own the games you're trying to play legally beforehand. Fans of playing 10 year old games in VR should also consider Dolphin VR, which you should also legally own the games for. Seriously.