No ref links, feel free to share others in comments.
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Ceek https://airdropalert.com/cms/join/CEEK Same
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dock.io https://app.dock.io/earn/promote easy, low payment, big project potential
Obirum https://bitcointalk.org/index.php?topic=2956357.new#new Easy
Odyssey http://ocoins.cc/bounty/register
Tradeplayz http://contest.tradeplayz.com/ Referral