Some currently active airdrop update 11 Jan:

Suchapp: http://vy.tc/eYNGc13 - very interesting airdrop campaign and solid project => definitely should keep an eye on 2018
Dividend https://www.dividend.cloud/airdrop.php
IOST Link
KMC: Telegram
OLXA: Link OLXA
Zeepin: https://www.zeepin.io/bounty/?r=MvB7P
Benebit: Link form
Polymath: https://polymath.network/
ConnectX: Link ConnectX
Upcoin: https://upcoin.com/
TIM: http://www.talking.im/airdrop/hsMsAobiqM

Follow the links to earn free coin of each project. Good luck to you all!

Update 12 Jan 2018:

Lightchain: Lightchain
Sp8de: https://www.airdropx.com/#join

Update 13 Jan 2018:
Sphere: Sphere - earn 50 coin just by signing up - this coin is listed already
CCRB: https://ccrb.io/ sign up to earn free coin
VIULY: viuly.io sign up account to earn 50 coin

Update 14 Jan 2018:
Swift demand: Based on the idea of basic income of country distribute an equal amount of money to people. Swift Demand distributes 100 swift/day to every member of the system equally. Coin will be used for purchases and consumed in the system.
The idea is interesting, although currently the system is still small and not much to purchase, but the growth speed is quick and if it could reach to a big scale, the potential will be pretty amazing. And by the way, 100 coins for free everyday => isn’t it good?

Link: Swift demand register => register account, verify and claim 100 coins distributed everyday

Update 16 Jan 2018:
Two potential projects I've just learnt about are opening their airdrop programs
Realchain
3 Simple Steps to be eligible for 10 RCT airdrop:
1. Join Realchain telegram https://t.me/realchain
2. Follow @RealChainFund Official Twitter
3. Submit your #ETH wallet address (not exchange address) to bot @realchainbot by messaging the bot PRIVATELY; Simply look for @realchainbot from the member list, and send message to the bot in private;
4. Tokens will start to be distributed on Jan 27th 11:59pm EST.

Shipchain:
Link: https://shipchain.io/ go to the airdrop section
Fill the Docs form to receive airdrop