A great source for books are the trash receptacles surrounding college dormitories at the end of the year. In fact, this is a good place to find pretty much anything that you might ever need, or even lots of stuff you don't. I found this book in the trash room of my dorm senior year. It's an especially remarkable treasure because it's an advanced manuscript signed by the author, wowza!
Dinner party freecycle
If you have stuff to get rid of, why not have a "who wants this junk that I'm getting rid of?" segment during your next dinner party? Everybody loves a party favor.
Craft Service
I helped out on a friend's film shoot and kindly volunteered to make the leftovers disappear after we wrapped. I tossed the pizza and bagels in the freezer, put the coffee in a container in the fridge for ice coffee tomorrow, stored the chips for the next time I need some crunch, and threw the sugar packets and cups into the drawer I keep for picnic and party supplies. Inside of five minutes, this craft service was stowed away for the next time I need to service a craft.
Catering
After catering an event, a friend of mine was saddened to see tray after tray of untouched food tossed out, so she brought me approximately 79 pounds of pesto pasta. I froze it in baggies, and have enjoyed a plate of it weekly for going on three months.
Home.
I got an early start on this frugan thing.
Stationery Stockpile
This is a good example of stockpiling refuse for future re-purposing. This yellow note came from a CocaCola tin that I acquired some 10 years ago. When at the last minute I was asked to put together a slideshow, I was trying to come up with a quick tactile way to present my contact info (phone number scribbled to acquiesce to mom's fears of identity theft). As ever, I went to my hold-for-later drawer (admittedly easier to have in Los Angeles abodes than in New York shoeboxes), and found these silly yellow paper slips. Pile that on a sheet of paper with my custom name stamp from 1991 and presto!