ocsdata.ncd.noaa.gov/OnlineViewer/
Another great source of free, US online charts at
http://sailvector.com/
Howard [Just Imagine] 31-Dec-1969
ocsdata.ncd.noaa.gov/OnlineViewer
has moved to
http://www.nauticalcharts.noaa.gov
Howard [Just Imagine] 25-Oct-2008