This is a contract used for buying and selling activities, with the help of an escrow.
This is a people registry where you map a person and his details to his ETH address.
This is a contract used for depositing. When someone deploys the contract he says how much does he want to lock his ETH.
This is a contract used for raffles. The owner of the contract can deploy it and set various parameters. Anybody can start the raffle after the minimum days have passed.