AstroGrid
Research and development project to produce a virtual observatory based on grid technologies. Site has news, forum and wiki areas allowing free and open collaboration on project.
http://www.astrogrid.org

The Joint Astronomy Centre
Services and support to enable astronomers to undertake research using the James Clerk Maxwell Telescope and the United Kingdom Infrared Telescope.
http://outreach.jach.hawaii.edu/

The Royal Observatory, Greenwich
An informative website from the home of the Prime Meridian of the world.
http://www.rog.nmm.ac.uk