Yippie Currency
I remember reading in ‘Steal this book’ a section about Yippie Currency the idea of exchanging money for coins that are of the same size and shape but of less of a value such as the urguayan 10 centismo being the same size as a quarter.
Thought something like this would come in handy in saving people money while at the same time taking it out of the greedy corporate owners pockets 
- URUGUAYAN 10 CENTISIMO PIECE
- works in many soda and candy machines, older telephones (3 slot types), toll machines, laundromats, parking meters, stamp machines, and restroom novelty machines. Works also in some electric cancerette machines but not most mechanical machines.
- DANISH 5 ORE PIECE
- works in 3 slot telephones, toll machines, laundromats, automats, some stamp machines, most novelty machines, and the Boston Subway. Does not work in soda or cancerette machines.
- PERUVIAN 20 CENTAVO PIECE
- works in new (one slot) telephone and some electric cancerette machines, but does not work as many places in the Uruguay, Danish and Peruvian coins.
- MEXICAN 10 CENTAVO PIECE
- works in new (one slot) telephones and some cancerette machines, but does not work as many places as the Uruguay, Danish and Peruvian coins.
- ICELANDIC 5 AURAN PIECE
- most effective quarter in the world, even works in change machines. Unfortunately, this coin is practically impossible to get outside of Iceland and even there, it is becoming difficult since the government is attempting to remove it from circulation.
Dime Size Coins
- MALAYSIAN PENNY
- generally works in all dime slots, including old and new telephones, candy machines, soda machines, electric machines, stamp machines, parking meters, photocopy machines, and pay toilets. Does not work in some newer stamp dispensers, and some mechanical cancerette machines.
- TRINIDAD PENNY
- generally works the same as Malaysian Penny.
New York Subway Tokens
- DANISH 25 ORE PIECE
- works in 95% of all subway turnstiles. A very safe coin to use since it will not jam the turnstile. It is 5/l000th of an inch bigger than a token.
- PORTUGUESE 50 CENTAVO PIECE
- the average Portuguese Centavo Piece is 2/1000th of an inch smaller than a token.
- JAMAICAN HALF PENNY, BAHAMA PENNY and AUSTRALIAN SCHILLING
- these coins are 12/l000th to 15/1000th of an inch smaller than token. They work in about 80% of all turnstiles. We have also had good success with FRENCH l FRANC PIECE (WWII issue), SPANISH l0 CENTAVO PIECE NICARAGUAN 25 CENTAVO PIECE.
Any others from around the world?
UK / Euro currency exchange possibly?