distributed.net is a loosely knit group of computer users from all of the world that is taking up challenges requiring lots of computing power (most notably the RC5, DES, and OGR cracking contests). It is simple to participate in the challenges by downloading and running their client software (which uses idle CPU time to complete its tasks).
Botan is a crypto library written in C++. It provides a variety of cryptographic algorithms, including common ones such as AES, MD5, SHA, HMAC, RSA, Diffie-Hellman, DSA, and ECDSA, as well as many others that are more obscure or specialized. It also offers SSL/TLS (client and server), X.509v3 certificates and CRLs, and PKCS #10 certificate requests. A message processing system that uses a filter/pipeline metaphor allows for many common cryptographic tasks to be completed with just a few lines of code. Assembly and SIMD optimizations for common CPUs offers speedups for critical algorithms like AES and SHA-1.
Libecc is a C++ elliptic curve cryptography library that supports fixed-size keys for maximum speed. The goal of this project is to become the first free Open Source library providing the means to generate safe elliptic curves, and to provide an important source of information for anyone with general interest in ECC.
Tutorial Environment for Cryptographic Protocols (TECP) is a tutorial and visualization environment for public key cryptography. It is intended for students of cryptography courses and can be used to improve understanding of modular arithmetic-based public key algorithms, and for lecturers who want to add some life to boring blackboard-and-chalk presentations about the topic.