  The influence of different types of disorder (both uncorrelated and
correlated) on the superfluid properties of a weakly interacting or dilute Bose
gas, as well as on the corresponding quantities for flux line liquids in
high-temperature superconductors at low magnetic fields are reviewed,
investigated and compared. We exploit the formal analogy between superfluid
bosons and the statistical mechanics of directed lines, and explore the
influence of the different "imaginary time" boundary conditions appropriate for
a flux line liquid. For superfluids, we discuss the density and momentum
correlations, the condensate fraction, and the normal-fluid density as function
of temperature for two- and three-dimensional systems subject to a space- and
time-dependent random potential as well as conventional point-, line-, and
plane-like defects. In the case of vortex liquids subject to point disorder,
twin boundaries, screw dislocations, and various configurations of columnar
damage tracks, we calculate the corresponding quantities, namely density and
tilt correlations, the ``boson'' order parameter, and the tilt modulus. The
finite-size corrections due to periodic vs. open "imaginary time" boundary
conditions differ in interesting and important ways. Experimental implications
for vortex lines are described briefly.
