Seismosurfing the web: http://www.geophys.washington.edu/seismobig.html
Southern California Earthquake Center: http://www.scec.org/
US National Data Center for nuclear monitoring: www.tt.aftac.gov
Institutes for Research in Seismology: www.iris.edu
Global seismology information: http://neic.usgs.gov/
USGS National Earthquake Hazards program: http://earthquake.usgs.gov/
US National Seismic Network: http://neic.usgs.gov/neis/usnsn/usnsn_home.html
US National Strong Ground Motion Program: http://agram.wr.usgs.gov
USGS Northern California Earthquake Program: http://quake.wr.usgs.gov/
Cal Tech seismological laboratory: http://www.gps.caltech.edu/seismo/seismo.page.html
Universtiy of California, Berkeley: http://www.seismo.berkeley.edu/seismo/Homepage.html
Scripps Institute, Univ. of Calif, San Diego, IDA web site: http://www-ida.ucsd.edu/public/welcome.html
Harvard University Moment Tensor Library: http://www.seismology.harvard.edu/
Columbia University, Lamont-Doherty Geological Observatory: http://www.ldeo.columbia.edu/LCSN/
University of Utah Seismic Networks: http://www.quake.utah.edu/
US Seismic Networks composite catalog: http://quake.geo.berkeley.edu/cnss/
Current Volcano activity: http://www.geo.mtu.edu/volcanoes/
Volcano workings and volcano seismology: http://vulcan.wr.usgs.gov
Every link known on seismology: http://pasadena.wr.usgs.gov/info/seismolinks.html