Resources:

Spoonflower fabric print on demand.
Spoonflower Flickr group
Zazzle custom printed shoes and clothing
Victoria Albert Museum Textile Education Resource
Creative Commons resource for images
Selvedge Magazine

Freeware imaging tools:
Photoshop like program: Sumopaint
Photoshop like program: Gimp.org
Vector program: http://inkscape.org/
Photoshop like program: http://www.getpaint.net/
Program that converts line drawings to vector based images: http://linetracer.sourceforge.net/
Copyright free images of the National Oceanic and Atmospheric Administration

Tiling applets:
taprats
Penrose Tiling Applet
Spiral Tiling Applet

(Thank you to Jeffrey Fried for sharing the above two applets)