Stamp machines had not yet updated yesterday, so one could still purchase "Forever" stamps at $0.45 and return them today for $0.46. Not very scalable, but good for over a 2% riskless return in 24-hours. Machines had as much as $900 per post office for 2,000 stamps and a $20 return. Add to that another $9 or so for the credit card rewards.
Disclosure: I have no positions in any stocks mentioned, and no plans to initiate any positions within the next 72 hours.
Additional disclosure: Chris DeMuth Jr is a portfolio manager at Rangeley Capital, a partnership that invests with a margin of safety by buying securities at deep discounts to their intrinsic value and unlocking that value through corporate events. In order to maximize total returns for our partners, we reserve the right to make investment decisions regarding any security without further notification except where such notification is required by law.