Tools

These sites have useful information for engineers and PCB designers.

PCB trace impedance calculator
http://emclab.mst.edu/pcbtlc2
Chart of screw sizes and clearance hole sizes
http://www.marfas.com/machinescrewtapping.shtml
Electronics industry standards
http://www.ipc.org
Mentor Pads site
http://www.mentor.com/products/pcb-system-design/design-flows/pads/
Altium Designer site
http://www.altium.com/products/altium-designer/en/altium-designer_home.cfm
Recommended PCB manufacturing company
http://www.westak.com/facilities/oregon.html
Recommended assembly and test company
http://www.qplpcba.com
PCB industry resource guide
http://www.everythingpcb.com