The FEMA Emergency Management courses (IS-100a, 700 etc) are
very good. These are mandatory these days for emergency
responders.
Twin Cities Amateur Radio Data. They are the sponsors of the monthly open workshops.
The place for radio-TNC cabling diagrams
KB8ZQZ's trivnetdb page- a modern TCP/IP + Packet +
D-Star capable LINUX replacement for ARES-Data ! We are
using Linux systems as D-Star back ends
The American Radio Relay League - the National organization of Amateur Radio: look up clubs, hamfests and other information.
Peter's D-Star site - he is one of our software architects
Alan's D-Star site - he has a set of linked repeaters
and some cool home-made L-band antennas and
duplexers/triplexers
Kelly has Citadel - open source mail and conferencing -
on our repeater sites