http://www.arrl.org/FandES/field/pscm/
This the Public Service Communications Manual of the American Radio Relay League(ARRL). It is in HTML but you can download it as a PDF file.
According to the web site “eHam.net is a community site designed and operated by and run for active Amateur Radio operators (hams). eHam.net is not just a website. It is the Internet's #1 Amateur Radio Community.”
Emcomm is the web site for WORLD RADIO RELAY LEAGUE® and the site says “Welcome...To the most complete source of Emergency Communications (EMCOMM) information on the Internet”
This is a very good site to get information about echolink and for a variety of echolink downloads.
http://www.safecomprogram.gov/SAFECOM/natlemergencycommplan/
If you are interested in reading the National Emergency Communications Plan from Homeland Security, here it is.
QRZ is regarded by most hams as a very good site for general ham radio information and call signlook-ups. It is also a good site to get help in upgrading your license and finding practice exams.
Here Are Seven Sites That Will Help You Get or Upgrade Your Ham Ticket
http://www.eham.net/exams/ Generate practice exams
http://www.qrz.com/testing.html Generate practice exams
http://aa9pw.com/ Generate practice exams
http://www.w8mhb.com/exam/ Generate practice exams
http://kb0mga.net/exams/ unique flash card mode
http://www.radioexam.org/ Lots of other info also
http://www.arrl.org/arrlvec/pools.html Total question pools
This site is the U.S. Geological Survey Earthquake Hazards Program. If you want earthquake information, this site is regarded as one of the best.
This is the site of the Los Angeles County Disaster Communications Service. You can see some of the history of how it has served the citizens of LA County and the tools and training it offers.
The Sheriff stations at Walnut/Diamond Bar and San Dimas have a very active group of volunteers. This page will tell you some specifics about that unit.