http://www.minorplanetcenter.org/iau/mpc.html
The Minor Planet Center at Cambridge, Massachusets, USA.
It is the official IAU center, responsible for the collection and dissemination of astrometric observations and orbits of asteroids and comets. The main publications are: the Minor Planet Circulars, containing astrometric observations, orbits, ephemerides, new numberings and namings of asteroids and comets; the Minor Planet Electronic Circulars, supplying information on unusual minor planets (including NEOs) and new discoveries.

http://neo.jpl.nasa.gov
NASA's Near-Earth Object Program Office site at the Jet Propulsion Laboratory.
A lot of various useful information on NEOs.

http://www.lowell.edu/users/elgb
Ted Bowell's home page, including ASTORB - the world largest catalog of asteroidal elements.

http://newton.dm.unipi.it/neodys/
NEODyS, the Near Earth Objects Dynamic Site of the University of Pisa.
Plenty of information on all NEAs, including their observations at numerous world observatories.

http://spaceguard.iasf-roma.inaf.it/
The Spaceguard Central Node. The pages of the Spaceguard Foundation, the NEO Science and the Spaceguard System.
The last page provides the tools for facilitating the observations and coordinating the work of various centers. The Priority List is among these tools.