Af-Arch is an N-tier development framework to quickly build high-quality distributed applications. It currently supports C and C# programming languages, which enables you to write client applications using them. It currently runs on GNU/Linux and Microsoft Windows, and is being used in production environments.
Bugzproxy is a C# client library for the upcoming Bugzilla Bugtracker WebService interface (part of Bugzilla 3.0). It provides an OO access to a Bugzilla server. The aim of Bugzproxy is to allow easy building of various clients that facilitate the integration of Bugzilla into the various C# tool chains. As the project's aim is to provide an efficient and intuitive OO API, the API probably will change in future revisions.
Caffeine is a free high-performance interoperability solution between the Java platform and the .NET framework, with special emphasis on the enterprise variants of such platforms. It makes software originally written for .NET available to the Java platform. It promotes library reuse between Java and .NET by transferring APIs across environments, and allows code written for one platform to run on the other platform with minimal performance degradation. It is powered by Mono, and runs on Alpha, Linux, Windows, Mac OS X, HPPA, SPARC, and s390 systems.
CryptSharp provides a number of password crypt algorithms: BCrypt, MD5 (and Apache's htpasswd variant), PHPass (WordPress, phpBB, Drupal), SHA256, SHA512, and Traditional and Extended DES. It also includes Blowfish, SCrypt, and PBKDF2 for any HMAC (.NET's built-in PBKDF2 implementation supports only SHA-1). If you are looking to store passwords, odds are CryptSharp will have the algorithm you want.