r/Cryptoairdrop is the reddit forum containing cryptocurrency airdrop information. Here you will find a plethora of information uploaded by the Reddit community.
The thread seems to be updated very often and when I visited it, there were new posts within the last minute. This may be a fantastic way to keep up to date and act quickly on the newest and most recent airdrop advancements.
With that said, you need to be extremely careful when using this forum. These opportunities are not vetted and there is little to stop nefarious posters from providing false information or worse, attempting scandalous behaviors.