I have been experimenting with making collage material by re-using existing papers. Newspapers, brown paper bags, magazine papers, and a discarded HUGE dictionary that someone left at the post office for the taking, have been my favorites.
One way I like to make collage papers is by gel printing. Here is a video about it. I will be teaching Monoprint Collage in Santa Fe this spring, and there are a few spaces available still. We will use the gel plate and other techniques for printing and painting collage papers, and then do and in-depth exploration of collage.
Sign up for the workshop here.