Plarn and tarn are eco-friendly ways to make yarn-like material.
Plarn is yarn made from plastic - usually grocery or garbage bags or the plastic they slip around newspapers to keep them from getting wet. Please see my older blog posts to find links for plarn projects.
Tarn is made from old t-shirts although you could make something similar from other items, like umbrella material, jeans, old sheets, etc.
Tarn is great to work with because t-shirt material can be cut without shredding and is soft when running through your fingers. It's strong enough to weave into a hammock - although it might be a little stretchy for a weight-bearing project. It is very versatile, being useful for knitting, crocheting, or weaving. It can be cut in narrow strips for smaller hooks and needles or thicker for larger hooks and needles. A throw rug could be made thick and cooshy while a bath mat could be worked from thinner strips to dry out more easily.
I don't have permission to copy anyone's photos for this post. For information on how-to and free patterns, please check www.youtube.com (Noreen Crone-Findlay is an authority on the yarn arts), www.ravelry.com, www.knittingpatterncentral.com, www.crochetpatterncentral.com, and many other websites and blogs. You an always type "tarn instructions" or "tarn patterns" into Images of your favorite browser and find tons of interesting ideas. Click on the ones you like and your browser will pop you into the website with the pattern you are curious about.
The sister project with this type of material is weaving, since tarn is thick enough to make into woven rugs quickly and easily. I once found a tutorial showing how to weave a round rug using a hula hoop as a frame. I've found that I can make a small throw rug by weaving between two legs of a card table. (Turn the card table on its side and use the top two legs.)
I found a picture of me weaving for a special event at the library.
Another technique for making rag rugs is shown at http://www.youtube.com/watch?v=rKJan2WBKFo. This video demonstrates a twined weaving technique.
If you are really ambitious, you could use tarn to braid a rug. The old way of braiding had you ironing all of the edges to the inside of the strip so they wouldn't fray. Tarn doesn't fray, making this project a whole lot easier.
So dig out those old t-shirts and a pair of scissors and have fun.