Whisper.sh - Whisper is the best place to express yourself online. Connect with likeminded individuals and discover the unseen world around you.

Friendica - Decentralisation - Privacy - Interoperability

Sayat - Sayat app is all about getting anonymous and honest feedback.

Pleroma - Pleroma is a free, federated social networking server built on open protocols.

Sarahah - Sarahah is a Social Networking Application for providing anonymous feedback launched in 2016 and available to use on iOS and Android platforms.

Mastodon - Mastodon is a decentralized, open source social network. This is just one part of the network, run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome!