Recycling Plastic Bags
My Recyled Bags has a great tutorial on how to cut the bags and connect the pieces.
Similar tutorial by Gooseflesh.
This is the method I prefer, though it makes a double-strand thickness.
If you prefer a thinner yarn, another method is to cut each bag into a spiral (like an orange peel).
Weavezine shows this method, and also gives a tutorial on weaving plarn.
Or perhaps the tutorial by Pie and Coffee will make more sense to you.
Recycled plastic totes are especially great beach bags--they can be rinsed off easily, and are long lasting.
They're also great for shopping bags (ironic, eh? Plastic shopping bags, reused and made into reusables).
They are also quite sturdy.
Wow, go figure--Creative Recyclers show how to weave a tube shape from plastic bags, using a plastic bottle as a prop.
This spool knitting technique (with real yarn) is also shown on Craftypod.
Atomic Shrimp used a handmade French bobbin and 25 plastic bags to knit this amazing tote
There are a lot of patterns out there, but here are just a few to get you inspired:
I loooove this crocheted tote from Marlo's Crochet Corner (instructions on her site).
I have just enough blue Walmart bags saved for the project.
For anyone who likes to use plastic bags for projects, there was a collective groan when Walmart switched from blue to ordinary white bags.
Crocheted tote tutorial on The Knitty Professors
When searching for free patterns, you can sometimes find crochet or knitting plastic tote/purse patterns under "bread bag".
Packages from bread and newspapers are thinner plastic, are often easier to work with, and give a finer look.
I especially like the clear bags--they give almost a crystalline accent to your projects.
My Recycled Bags has a ton of patterns available, including Bread Bag Tote
Also from My Recycled Bags, a Granny Square Motif Tote
There seem to be fewer knitting tutorials out there, but almost any knit or crochet pattern can be adapted to use with plarn.
Also check youtube for video tutorials.