Here is a list of puzzles created on Ethereum.
For now, the contract is available only on the Rinkeby Test Network. Please switch your metamask to the right network before playing
You can enter a puzzle and try to solve it by paying a fee. The fee will be added to the total reward. The reward is split between the first winner and the creator of the puzzle.
You have also the possibility of creating your own puzzle.
source code : https://github.com/falj/puzzle
Feel free to donate here