Six Exploding Knots
Covers six knots that untie easily, including the Sliding Butterfly, Double Carrick bend, and Clove Hitch Biting a Bight. Step-by-step illustrations with instructions and a table of properties.
http://www.earlham.edu/~peters/writing/explode.htm

The Lehigh Group
Covers common marine knots, plus the Hangman's knot, the Scaffold knot, and the Gallows knot. Illustrations and common uses.
http://www.lehighgroup.com/KNOTS.HTM

Sophia-Antipolis Speleogical Society
Covers common caving knots including the double figure-8 on a bight and the farmer's knot. Illustrations.
http://www-sop.inria.fr/agos-sophia/sis/Techniques/knots.html

University of New England Mountaineering Club
Covers the Alpine Butterfly, Bowline, Clove hitch, and Fisherman's knot. Animation and common uses.
http://www.une.edu.au/~unemc/alpbutt.htm

5.10 Climbing Club: Double Butterfly
Explanation, illustrations, and instructions.
http://five.ten.tripod.com/butter.htm

Rec.crafts.knots FAQ
Frequently asked questions for the newsgroup, covering resources, recommendations, and links.
http://www.msen.com/~pwmeek/knots/knot-faq.html

The Prusik Knot
Discussion, comments, and tips regarding use for both sailing and climbing. History.
http://fmg-www.cs.ucla.edu/geoff/prusik_knot.html

Blue Ridge Mountain Rescue Group
Covers climbing and rescue knots including how to make a seat harness from webbing and the bowline-on-a-coil. Photos and instructions.
http://brmrg.med.virginia.edu/knots/knots.html

Ropeworks
A book of knots, hitches, splicing, lashing and rope making.
http://www.northnet.org/ropeworks/index.html

Best Knots for Fishing and Outdoors
Illustrations and instructions for a large number of knots used in fishing, boating and paddling.
http://www.netknots.com

Notable Knot Index
New, useful, and interesting bends, loops, hitches, and knots.
http://www.geocities.com/roo_two/knotindex.html

Ropers Knots Pages
Index of knots with links, illustrations, and descriptions.
http://www.realknots.com/

Team Whiskers Knots
Catfishing Team. Includes information on baits, knots, rigs, tackle, recipes, and tournaments.
http://teamwhiskers.tripod.com/knots.html

Alrama's Knots
Animated graphics of several knots being tied.
http://alrama.tripod.com/cgi-bin/list.pl

Ian's Shoelace Site
Illustrations and instructions. Including common, faster and more secure knots. Also a section on different methods of lacing shoes.
http://www.fieggen.com/shoelace/

Climerware
Analysis of the strength loss caused by using a girth hitch. Climbing variations of the girth hitch, the dogvine, the mule knot, and the Figure-8. How to tie a bowline and clove hitch one-handed.
http://www.climerware.com/knot.shtml

Knot Knotes
Trivia, jokes, records, projects, and games. Knot basics. Downloadable fonts.
http://whatknot.tripod.com/knots/knot.htm

Caving Knots
Illustrated guide to the most commonly used knots in underground exploration.
http://www.geocities.com/knotsforcaving/

Knot Tying DVD
Sells a video (VHS/DVD) showing 47 knots and 6 splices tied from the user's perspective. Also gives information on making and caring for ropes. Language and Subtitle options: English/Spanish.
http://www.knottyingvideo.com/

Grog's Animated Knots
Knots for boating, climbing, and fishing with clear animations.
http://www.animatedknots.com/

Ruckus Society
Short climbers' knots manual.
http://ruckus.org/article.php?list=type&type=21

The Knotting Dictionary of Kännet
Covers some common and some uncommon knots, including the Reef knot, Square knot, Sheepshank, Simple Simon Over, Monkey's Fist, and Vice Versa. Illustrations and common uses. What the knot is called in other languages. User-submitted comments.
http://korpegard.se/knot/