A wonderful gift from the tooth fairy. This origami box made from 2 dollar bills contains a tiny note and some coins and even glitter, because after all it came from the tooth fairy.
The instructions for the box are no longer available on the original site, but can be found on archive.org. They're reproduced here for stability.
This box is made from two new crisp bills. Older, softer ones are harder to work with. For this design to work, the folds should be fairly precise, and perpendicular to the edges of the bill in order to make a rectangle.
Lay the first bill face up. Fold the bill in thirds lengthwise. Gently unfold these folds, referred to as third folds they will be used later.
Fold the bill top-to-bottom just to the right of the portrait, then unfold. Repeat just to the left of the portrait. These are portrait folds. Note that the third folds oppose (are perpendicular to) the portrait folds.
Starting at the top left corner, close the top third fold to about 90 degrees. Lift the right edge of the bill to the right of the right portrait fold up while holding the top third fold in place, allowing the third fold to close completely to the right of this corner.
Inside this corner will be a remaining portion that you will crease along the natural 45 degree line to complete the corner.
Complete the previous step for the other three corners. You will have two "tabs" sticking up on the left and right sides.
You should now have an open box.
Fold the second bill to make the cover lengthwise so that the width matches the widest portion of the open box just made. You need two width folds
Holding one end of the cover across the bottom of the open box, find the point which matches the corner of the open box and fold at that point.
After folding, open the fold to 90 degrees, hold the cover back in place, and find the point for the next corner of the open box as the cover wraps around. These are wrapping folds Repeat this process until the cover wraps over itself (four folds).
The end cover fold puts the remainder of the long side inside the wrapping folds. Refold the wrapping folds holding the long side in place to crease it at the correct points.
Slide the open box inside the cover before closing the cover tightly, or close the cover with the open box already inside. In either case you are done.