  We present a survey of diffuse O VI emission in the interstellar medium
obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE). Spanning 5.5
years of FUSE observations, from launch through 2004 December, our data set
consists of 2925 exposures along 183 sight lines, including all of those with
previously-published O VI detections. The data were processed using an
implementation of CalFUSE v3.1 modified to optimize the signal-to-noise ratio
and velocity scale of spectra from an aperture-filling source. Of our 183 sight
lines, 73 show O VI 1032 emission, 29 at > 3-sigma significance. Six of the
3-sigma features have velocities |v_LSR| > 120 km/s, while the others have
|v_LSR| < 50 km/s. Measured intensities range from 1800 to 9100 LU, with a
median of 3300 LU. Combining our results with published O VI absorption data,
we find that an O VI-bearing interface in the local ISM yields an electron
density n_e = 0.2--0.3 cm^-3^ and a path length of 0.1 pc, while O VI-emitting
regions associated with high-velocity clouds in the Galactic halo have
densities an order of magnitude lower and path lengths two orders of magnitude
longer. Though the O VI intensities along these sight lines are similar, the
emission is produced by gas with very different properties.
