Just some food for thought...
http://stop-emp.com/index2.html
They have white papers and such discussing EMP effects.
A good read was the:
CRS Report for Congress
High Altitude Electromagnetic Pulse (HEMP) and High Power Microwave (HPM) Devices: Threat Assessments -
http://stop-emp.com/crs.pdf
Especially the sections dealing with Private Sector Vulnerability and Military Vulnerability.
Also of good read was the US Congressional EMP Commission report -
http://stop-emp.com/EMPCExecRpt_Final072204.pdf .