Check your office copier to see if it can handle two-sided copies. If possible, set it as the machine's default mode. Making double-sided copies not only saves trees, but it can also save you up to $60 per month.
If every business in Washington, D.C. with less than 500 employees switched to double-sided copies for five years, the savings would be enough to hire more than a thousand interns at $10 per hour.
Sources:
Natural Resources Defense Council
New York City Waste Less
U.S. Small Business Administration (PDF)