Four Barrel, right by my gym. I saw them throwing them out one morning and snatched them up! You could probably ask your local cafe if they'd be willing to give them to you...
And then for the sake of time, I used some pre-stretched canvases. You can find them at any art supply store like Blick, but I got mine from Cliff's Variety.
To help make them functional bulletin boards, I added a layer of thin quilt batting before stapling the burlap over the canvas.
In some cases, the effect was purely decorative:
But in another case, the board will actually be used for hanging some jewelry:
I really liked how the green accent of this coffee sack matched the jewelry box above the dresser. It's going to look great with necklaces and earrings pinned to it--a fun and glam way to use burlap!