  The advanced capabilities of the Chandra and XMM-Newton observatories mean
that, for the first time, the detailed study of the brightest point-like X-ray
sources in nearby galaxies outside of the local group is a realistic aim. Here,
we present the results of a Chandra ACIS-S study of two of the nearest and
brightest sources in the rare ultraluminous (L(X) > 10^39 erg s^-1) X-ray
source (ULX) class, NGC 5204 X-1 and NGC 4559 X-1. When considered with new
optical integral field spectroscopy data this provides powerful diagnostics as
to the nature of these sources, in particular suggesting that NGC 5204 X-1 is a
high-mass X-ray binary, and showing new evidence linking it to the Galactic
microquasar phenomenon. We also find that both ULX appear to be located in
cavities in emission-line gas nebulae that surround the sources. In addition,
we present the results of a Chandra observation of the interacting galaxies NGC
4485/NGC 4490, a pair of late-type spiral galaxies that, remarkably, contain a
total of six ULX. We identify one as a supernovae, and the remainder as
probable black hole X-ray binaries. All six are located in star formation
regions, underlining the emerging link between ULX and active star formation
activity.
