kumihimo

Various online craft tools exist, usually for colour planning or design generation. These are the ones I know about:

Needlework

Cross Stitch Charts from photos
My Photo Stitch a free service that takes photos you upload and gives you a cross stitch chart using (last I checked) DMC colours

Knots

Turk's Head Cord length calculator
http://turkshead.50webs.org/
Turk's Head Knot designer
http://data.oreilly.com/jallwine/knots/
Globe Knot Core Calculator
http://khww.net/gkcc.php
Turk's Head Design Playground
http://web.meson.org/crafts/TH/TH.html

Kumihimo Braiding

8 strand kongo gumi colour planner
http://www.lythastudios.com/123bead/kumiplanner.html
16 strand kongo gumi colour planner
http://craftdesignonline.com/kumihimo/
A colour planner for the 7-loop Spanish finger loop braid
http://www.islandlife.heliohost.org/cgi-bin/fingertips.pl