Signal-Integrity Links

http://www.sigcon.com/ (recommended by Fred)

http://www.nesa.com/

http://www.sigrity.com/

http://www.ultracad.com/ (careful here)

http://www.qsl.net/wb6tpu/si-list/ this is the signal integrity mailing list archive; lots here, good and bad)

http://www.dsmith.org

http://www.research.ibm.com/journal/rdimg.html Sept/Nov 1999 Issue has several papers directly relevant to digital systems engineering

http://www.national.com/rap/Story/0,1562,18,00.html Excellent discussion by Bob Pease of coupled noise in analog systems, how to identify sources, and reduce it. Many of these techniques have wide applicability

Impedance calculation for various PC board stackups: http://www.icd.com.au/board/

Following Links identified by Michael Wrighton:

Wire over ground inductance calculation: http://emcsun.ece.umr.edu/new-induct/g-wire.html try this one with h=s and h=(s+delta)
Microstrip : http://www.emclab.umr.edu/pcbtlc/microstrip.html
Stripline : http://www.emclab.umr.edu/pcbtlc/strip.html

Eric Bogatin Web Page ("Rules of Thumb I have Known and Loved" and more) www.bogatinenterprises.com

Three papers on Digital Systems Engineering in the IBM Journal:
Self-Timed Interface: MCM Technology; Chip Integration Methodology

Papers on high-speed (up to 9.6Gbs) signals on PC board traces and connectors (AMP Corp) (select conference papers).