  We present high-precision timing of five millisecond pulsars (MSPs) carried
out for more than seven years; four pulsars are in binary systems and one is
isolated. We are able to measure the pulsars' proper motions and derive an
estimate for their space velocities. The measured two-dimensional velocities
are in the range 70-210 km/s, consistent with those measured for other MSPs. We
also use all the available proper motion information for isolated and binary
MSPs to update the known velocity distribution for these populations. As found
by earlier works, we find that the velocity distribution of binary and isolated
MSPs are indistinguishable with the current data. Four of the pulsars in our
observing program are highly recycled with low-mass white dwarf companions and
we are able to derive accurate binary parameters for these systems. For three
of these binary systems we are able to place initial constraints on the pulsar
masses with best-fit values in the range 1.0-1.6 M_sun. The implications of the
results presented here to our understanding of binary pulsar evolution are
discussed. The updated parameters for the binary systems studied here, together
with recently discovered similar systems, allowed us to update previous limits
on the the violation of the strong equivalence principle through the parameter
|Delta| to 4.6x10^-3 (95% confidence) and the violation of
Lorentz-invariance/momentum-conservation through the parameter |hat{alpha}_3|
to 5.5x10^-20 (95% confidence).
