Stuart Prescott's List of international Synchrotron SAXS & SANS Facilities (NB: still under construction! Submissions welcomed) Or a map.
This is a community effort. If you notice a neutron or synchrotron X-ray source missing please submit the details.
World Directory of SANS Instruments
The Xray sources portal is a good place to start for information related to Synchrotron X-Ray news and information
The new neutron source portal is now active and a good place for information and news releated to neutron science. At this time the old neutron site maintained by Argone National Lab is still available.