VorpX is (was; see update below) the only software on the market that we know of that lets you play games on an Oculus Rift developer kit that were never meant for VR. The last update it received was in April to support Grand Theft Auto V. When Oculus released Oculus Runtime 0.7, updating to the latest version meant losing the ability to use the vorpX drivers. It took the company some time, but vorpX 0.9 landed just in time for the Oculus Runtime 0.8 release.
The previous incarnation of vorpX, version 0.8.1, was a quick update to add support for GTA V, but this update has far more to it. The team working on the driver added and improved many features.
Direct Driver Mode is a given with the Oculus Runtime 0.7, as support for Extended and Direct Modes have gone the way of the Dodo. Asynchronous Rendering is now supported, which vorpX said significantly enhances the experience if you can't reach the desired 75 FPS (DK2) or higher. The driver now has a feature called Crystal Image that enhances the image quality of injected VR games. VorpX claimed the visuals are on par with native VR games with this enhancement technology.
The latest version of the driver added support for arbitrary resolutions. VorpX can support any resolution your computer can output. The company said that all games support this feature, and it can improve FOV issues in some games by choosing 4:3 or 5:4 aspect ratio resolutions.
VorpX 0.9 includes Dedicated Video Player Mode, which allows you to play 3D movies through a Rift HMD. VLC and MPC-HP both have profiles that support this function. Windows 8 and 10 users also get the benefit of an included desktop app that lets you browse the Internet or watch YouTube in VR. It also lets you launch vorpX games from within it.
VorpX already had a fairly comprehensive list of supported games. The driver works with over 80 first person games in full VR, and it has a Virtual Cinema Mode that lets you play non-first person games on a virtual big screen. The Virtual Cinema Mode officially supports close to 100 games, but vorpX said many games will work out of the box. VorpX 0.9 added five more games to the Virtual Cinema support list, including the Witcher 3, and eight more games with full immersive VR support, including Crysis 3.
There were several other improvements and changes made to the vorpX driver. You can find the full list here.
The vorpX driver sells for $39.99 and can be purchased through vorpx.com.
Update, 10/23/15, 4:27pm PT: VorpX was the only software I knew about, but this afternoon Neil Schneider from the Immersive Technology Alliance informed me of a comparable driver called Vereio Perception which has actually been around for some time.