Writing an application that needs to connect to SFTP servers? Use one of the following libraries.

Disclaimer: This site was created by developers of one of components listed below. This is why you will not find here review or detailed comparison charts of .NET components. Read The pitfalls of comparison charts blogpost by Lukas for more reasons why we don't find comparison charts helpful. In short - you have to check if the specific component is good for your specific development habits and your specific usage scenario.

.NET components

For developers working in C#, F#, VB.NET or other dotnet languages ...

Rebex SFTPSFTP library from creators of this site. Under continuous improvement since 2006. Runs on .NET on Windows, Linux and OS X, .NET CF, Xamarin.iOS, Xamarin.Android. Pure C# code.
Bitvise FlowSSH Library
ComponentPro SFTP and SCPA .NET library based on stolen code. ComponentPro is currently sued for copyright infringement.
Granados SSHAbandoned opensource project hosted on SourceForge. Last update in 2004.
Chilkat SFTP
Kellerman SFTP Library
nSoftware SFTP ComponentAlso known as IPWords SFTP
Secure BlackboxUsed to be called Eldos Secure Blackbox. Now owned by /n software.
SharpSSHOpensource project hosted on SourceForge. According to one StackOverflow post, it's a direct port of Java (JSch and JCE) libraries. See other StackOverflow post about SharpSSH.
SSH.NETOpensource project originally known as sshnet.codeplex.com. Now on GitHub.
WinSCP libraryWrapper around scripting interface of popular SFTP/SCP Windows client.
Xceed SFTP

Java components

Apache MINANetwork application framework with SFTP/SSH support.
Ganymed SSH-2Open source but no longer maintained.
JAdaptive Java SSH Client APICommercial Java SSH implementation derived from the J2SSH open source project.
JCraft JSchImplementation of SSH and SFTP in pure Java. Open source.
Maverick Synergy Java SSH APIOpensource SSH API
n/Software SFTP Component
SecureBlackBoxUsed to be called Eldos Secure Blackbox. Now owned by /n software.
SSHJImplementation of SSH and SFTP in pure Java. Based on BouncyCastle crypto library. Open source.