i've gotten a few questions online about where i get stuff for my collages. most of the things i use are either free or inexpensive. one place that i go to in san francisco is called SCRAP- which stands for scrounger's center for resusable art parts.
SCRAP gets all kinds of donations, such as paper, fabric, tiles, cards, books, beads and more. What's great about it is that the place is well organized into aisles and it's so much fun to browse because you never know what you're going to find. i always enjoy sifting through the boxes of photos and stocking up on envelopes and ephemera. it's a great way to get a variety of things for art, in a inexpensive way.
one tip if you have a chance to go:
don't bring large bills, they may not have enough change.
if you're ever in san francisco, definitely check it out!
scrap also has a links page, with links to other reuse centers.