Double your ether by Doubler contract! Contract code is being executed by the Ethereum world computer, which is to say that thousands of nodes around the world run code in lockstep. This is really, really slow, but has the advantage of making contract independent of any single controlling entity. Instead, contract functionality is transparent and the blockchain enforces, that it will always be executed exactly as specified.
You can take a look at contract source code, but the gist is, that by sending from 1 to 50 ETH to contract address, you are entered into the pyramid and stand to double your money if there are deposits after you (minus a 2 % fee, to be exact). Participants' funds are never under the control of the creator, but are instead held by the Doubler contract.
http://doubler-ethereum2.rhcloud.com/
