Airdrops and bounties are popular here. You are free to choose how to join for free depending on the appropriate task. Coinbase created sweepstakes - an option similar to the previous form of affiliate marketing, like a survey, but they may have included an incentive "$100 transaction" as a form of baiting customers. . sweepstakes - not part of the official bounty/airdrop category.
Choose jobs HERE]https://bitcointalk.org/index.php?board=238.0]HERE, it will probably create more value and optimism.