CryptPad is a private-by-design alternative to popular office tools and cloud services. All the content stored on CryptPad is encrypted before being sent, which means nobody can access your data unless you give them the keys (not even us).

Noise is a framework for crypto protocols based on Diffie-Hellman key agreement. Noise can describe protocols that consist of a single message as well as interactive protocols.
Used in WireGuard https://www.wireguard.com/

AONT = All Or Nothing Transforms = a secure way to transmit a document to a recipient in such a way that the recipient either gets the entire unmolested document in originally submitted form, or nothing at all. This idea goes back to Ronald Rivest of MIT. Very clever idea. It is crypto without being crypto in a legal sense.
See also https://github.com/dbmcclain/Math, https://github.com/dbmcclain/LispPlotter, https://github.com/dbmcclain/EBU-R128 and probably more.

NeoPG is a modern replacement for GnuPG 2
NeoPG starts as an opinonated fork of GnuPG 2 to clean up the code and make it easier to develop.
We want to provide a stable and extensible API for application developers, too.
Eventually, we will add new ways to use OpenPGP that make it accessible and usable.
As of 2021-12-06, the domain is no longer in use.

Abstract.
ElsieFour (LC4) is a low-tech cipher that can be computed by hand;
but unlike many historical ciphers, LC4 is designed to be hard to break. LC4 is intended for encrypted communication between humans only, and therefore it encrypts and decrypts plaintexts and ciphertexts consisting only of the English letters A through Z plus a few other characters. LC4 uses a nonce in addition to the secret key, and requires that different messages use unique nonces. LC4 performs authenticated encryption, and optional header data can be included in the authentication. This paper defines the LC4 encryption and decryption algorithms, analyzes LC4’s security, and describes a simple appliance for computing LC4 by hand.

An extended version called LS47 can be found on https://github.com/exaexa/ls47, which includes a 3D-printable model of the tiles.

Monocypher is an easy to use crypto library inspired by libsodium and TweetNaCl.

Cryptocat is free software with a simple mission: everyone should be able to chat with their friends in privacy.

   Open source. All Cryptocat software is published transparently.
   Encrypted by default. Every message is encrypted, always.
   Forward secure. Chats are safe even if your keys are stolen.
   Multiple devices. Devices receive messages even when offline.
   File sharing. Securely share files with friends.

Available for Windows, Linux and Mac.

Open source (MIT licensed), available for iOS, Android, Windows, OS X and Linux.

Protect emails, files, hard drives, server certificates and online accounts using cryptography. Your secret keys are always stored securely in the Nitrokey hardware and can't be stolen. The device is PIN-protected and is secured against hardware attacks. Backups protect against loss.

Uses a touch screen.