Chilean, Modulab Studio uses PVC from old advertising banners to design and create unique messenger bags from entirely recycled materials. Based loosely on the same core concept as Freitag's bags (which make use of dump truck vinyl tarps), the Modulab's are unique, recuperating a great deal of the plastic used in outdoor advertising in their manufacture.
Designer Pamela Castro, responsible for the firm, says "at Chile it's kind of complicated to work with recycling, as consumers reduce value to the design work and think that a product built with re-utilized materials should have minimum prices", that's why these kind of work in judgmental places is so valuable. The studio also works with accessories from hardware elements, such as nuts and washers.
As for Freitag bags as mentioned above...
Swissies Markus, Daniel Freitag designed these in '93. Trucks in Europe don't have solid walls. Instead they stretch tarps across the openings. These bags are made from those tarps after they are no longer useful. Also made with recycled bike tubes (for the piping) and recycled seatbelts. Every bag is unique. Very durable, easily repairable. Waterproof. Some are expandable. You can even build your own bag online! You choose what your bag will look like by placing a pattern over a unique tarp (virtually). Their facility in Tunisia employs handicapped people.