.NET Communication Library
The .NET Framework lacks support for some network protocols. With Smilla’s .NET Communication Library, developers can add NNTP to their .NET apps. It is written in C# and is distributed under the GNU Lesser General Public License.
cryptlib
Security toolkit with strong encryption and authentication. Supports many algorithms for symmetric/asymmetric encryption, authentication, and hashing. Free for non-commercial/shareware projects. Written in C. ActiveX and C++ wrappers are available.
CSpot SMTPClient
Bossware’s SMTPClient is a .NET SMTP client for adding outgoing email to apps and to Web pages. It doesn’t use .NET’s resource-hungry System.Web.Mail, which is merely a wrapper for CDONTS and CDOSYS. Written in 100% managed C# and CLS compliant.
FreeTextBox
The FreeTextBox control provides a WYSIWYG HTML editing environment for ASP.NET (Web Forms) Web pages. Visitors can edit text and click on buttons to format their text. The control is written in C# and has many options for customization.
FTP Component
.NET lacks FTP classes. KCommon FTP component lets programmers build .NET apps so users can send or receive files via FTP. Supports synchronous and asynchronous transfers. Supports passive but not active mode. Written in C#. Doesn’t support proxies.
Garbe.Sound Audio DSP
A digital audio processing class library for .NET that lets developers create their own sound filters or use the ones implemented by the author, such as Gain, Delay, and Reverb, as well as the ability to read and write .WAV files.
Lumisoft UI Controls
Lumisoft’s UI Controls 0.11 contains over a dozen basic flat controls for Windows Forms apps. The controls can be configured using the Property tab in VS.NET, but lack advanced WYSIWYG design-time support and databinding. Seems somewhat buggy.
MenuXP
MFC classes to add flat, non-3D, “water-color” Office XP-style UI controls to MFC apps. They have no raised edges, do not look “pushed in” when clicked, and are not “shadowed” (except for menus).
OpenSSL
Open SSL 0.9.7c lets applications use Secure Sockets Layer (v2/v3), Transport Layer Security (v1), and a general-purpose cryptography library, for data integrity, authenticity, and privacy security features. Perl or Cygwin needed for Win32 compile.
SourceGrid
SourceGrid is a basic .NET grid control. It allows simple data to be displayed without relying on XML. Useful for simple apps, it lacks databinding, WYSIWYG design-time and printer support, as well as grouping and master/detail capabilities.