www.pcbstandards.com
Lots of helpful info, libraries, vb scripts for PowerPCB

Mentor Graphics (was Innoveda)
Lastest owners of my favorite PCB layout software

IPC
the standards people for the pcb industry

IPC SMT Land Pattern Calculator
pattern dimensions per IPC-SM-782

Printed Circuit Design and Manufacture magazine
must read periodical for PCB designers

Merix Corporation Application Notes
great resource for design guides and
application notes

High Speed Digital Design
articles about design issues

Altera Corp Design Guidelines
info on high speed and BGA layout

Ultracad Design
use their site for great info and calculators,
but send your design work to me  ;-)