I think one of the most useful examples of the Social Construction of Reality (Berger and Luckman) is money. I had for some time, in my classes, discussed the notion that there really is no money. And there isn't. Proving that, or at least leading substantive support to the idea, however is a bit tricky. Using a paper dollar as an example, and questioning the students as to what it "really" is (paper), and that it only has value because we ascribe value to it is good up to a point.

Until I ran across an NPR podcast of "This American Life" that really set the story straight. I have since lost the original but have found two that essentially go together. The transcripts are below.
One is titled "The Island of Stone Money," and the other is titled "How Fake Money Saved Brazil." You must check them out.
Survival Guide Manual
Excerpt from Social Problems
This transcript from an NPR podcast of "This American Life" titled "The Island of Stone Money," demonstrates that it doesn't matter what you use for a symbol of your currency and that it doesn't matter where it is or even if it has any real substance. (The word "real" becomes very important in the next story.)
This second NPR transcript explains how the economy of Brazil was saved through merely tricking the public as to what their money was actually worth and that it could now be made stable, regardless of its wild history of inflation. A trick, a lie, or merely a belief.