This has been around for a while, but I’m re-mentioning it because it’s not really linked anywhere: Simon ‘corecode’ Schubert has a version of the FreeBSD NVIDIA video driver that should work on DragonFly: http://gitweb.dragonflybsd.org/~corecode/nvidia.git.  It should be possible to clone from that link, build the code, and use it.  (Untested by me – if you’ve done it, some explicit instructions would be helpful to others.)