Esperantus Web Translator
Esperantus help you localizing a web site. It is written in C# any MsNet and Mono. Provides abstract data layer for keys and countries, globalized WebControls with multiple assemblies, Language Switcher, Money, Section 508 controls and much more.

Geotools.Net
Geotools.Net is a set of .net class useful when handling geographic information. The project started as port from Java to C# of JTS 1.2.

LDAP Libraries for C#
LDAP Libraries for C# enables you to write applications that access, manage, and update information stored in Novell eDirectory™ or other LDAP-aware directories. These classes are based on the IETF LDAP Java Application Program Interface.

nBASS
nBASS is a .NET wrapper for the BASS sound library implemented as a component with full designer support.

NFop
NFop is a Formatting Objects Processor (FOP) for XSL-FO that runs on the .NET Framework. It is a port from the Apache XML Project's FOP Java source to .NET's Visual J#. This makes it great for pure .NET reporting modules.

Nini
Nini is the uncommonly powerful .NET configuration library. The goal of this project is to provide developers with a tool that makes it easy to write highly configurable applications in a short amount of time.

XML-RPC.NET
XML-RPC.NET is a library for implementing XML-RPC Services and clients in the .NET environment.The library has been in development since March 2001 and is used in many open-source and business applications.