Sorry, but these links are badly in need of reviewing and updating. I hope to get around to it soon.
Radiocommunications Agency legacy site
UK National Physical Laboratory
US National Institute of Science and Technology (NIST)
Radio Society of Great Britain (RSGB) EMC Committee
ARRL EMC Committee (association of US amateur radio operators)
IEE EMC Professional Network
University of Missouri-Rolla EMC Laboratory
Gigatest Labs, Inc. (Eric Bogatin)
High Frequency Measurements Web Page (Doug Smith)
UltraCAD, Inc. (Douglas Brooks)
Signal Consulting, Inc (Howard Johnson)
Xilinx Signal Integrity Centre
US Military Joint Spectrum Centre
UK Department of Trade and Industry, Standards and Technical Regulations Directorate, downloadable documents
CE Marking Information and Service Center
Conformance
Elmac Services Ltd
aCEmark Europe Ltd
Emlib
The IEC’s “EM Zone”
Clemson University Vehicular Electronics Laboratory