A Knot Theory Primer
Comprehensive knot theory site focusing on the knot classification problem and knot tabulations. Has a tabulation of knots with up to 12 crossings.
http://www.inst.bnl.gov/~wei/contents.html

History of Knot Theory
Biographies of early knot theorists. Many early papers on knot theory (in pdf format) including papers by Tait, Kirkman, Little and Thomson.
http://www.maths.ed.ac.uk/~aar/knots/index.htm

The Geometry Junkyard: Knot Theory
A page of links on geometric questions arising from knot embeddings.
http://www.ics.uci.edu/~eppstein/junkyard/knot.html

Knot Theory Group University of Liverpool
Links to preprints and to programs written in pascal for doing knot calculations.
http://www.liv.ac.uk/~su14/knotgroup.html

Pewag
Offers snow chains, gear-lifting chains, and drive chains.
http://www.pewag.com

The Knot Theory Home Page
Elementary introduction to knot theory. Covers the existence of knots, Reidemeister moves and colorations.
http://library.thinkquest.org/12295/

Drives & Drives
Roller Chains, Sprockets, Couplers, Conveyor Chains, Slat Chains, Backstops, Precision Roller Chains, Heavy Series Roller Chains, Straight Sided Plate Chains, Standard Chains, Double Pitch Chains, Mayr Products, India
http://www.ddrives.com

Journal of Knot Theory and Its Ramifications
Journal of Knot Theory and Its Ramifications intended as a forum for new developments in knot theory, particularly developments that create connections between knot theory and other aspects of mathematics and natural science.
http://www.worldscinet.com/jktr/jktr.shtml

Megamath Knot Theory Page
An introductory overview of knot theory.
http://www.c3.lanl.gov/mega-math/gloss/knots/knots.html

A Circular History of Knot Theory
Starting with the flawed theory of Kelvin's knotted vortex to the work of Thurston, Jones and Witten, knot theory has circled back to its ancestral origins of theoretical physics.
http://www.math.buffalo.edu/~menasco/Knottheory.html