LibreSSL Portable is a free version of the SSL/TLS protocol forked from OpenSSL, and developed by the OpenBSD project. LibreSSL is developed as part of the OpenBSD system, with lots of ancient cruft and security woes already fixed. The portable version for other Unices is developed alongside.
The OpenSSL Project is a collaborative effort to develop a robust, commercial-grade, fully featured, and Open Source toolkit implementing the Secure Sockets Layer (SSLv2/v3) and Transport Layer Security (TLSv1) as well as a full-strength general-purpose cryptography library.
PolarSSL is a light-weight cryptographic and SSL/TLS library written in C. PolarSSL makes it easy for developers to include cryptographic and SSL/TLS capabilities in their (embedded) applications with as little hassle as possible. Loose coupling of the components inside the library means that it is easy to separate the parts that are needed, without needing to include the total library. PolarSSL is written with embedded systems in mind and has been ported on a number of architectures, including