Knots are amazing things…
You can use them to secure your thread as you sew, or turn them into a decorative embroidery accent.  They can be used to make everything from horse equipment from jewelry.  Humans have been using everything from hair, leather, rawhide and natural fibers since… well, the dawn of humanity to make knots.
I recently came across two very unique ways of using knots to create something decorative and useful at the same time.
The first one is this great tutorial from Threads Magazine, how to make a knotted belt:

The knotting pattern looks awfully complex when you look at this …read more

I’ve used drawings of knots (celtic interlace) for a couple of projects here.  I just found this great site for making three-dimensional decorative knots!
It’s called “Chinese Knotting” and has detailed instructions for lots of different decorative knots.
Wouldn’t this knot be beautifully stitched onto a garment or used instead of buttons?

Or what about using this one to decorate a wall-hanging… or another guestbook