Dropbear SSH Server and Client is an open source software application used for secure shell (SSH) remote login, secure file transfer, and secure communication between two computers. It is a lightweight, small-footprint SSH server and client and is used in embedded systems. It supports a variety of authentication and encryption methods, including RSA and DSA public keys, as well as password authentication. It also supports compression for faster data transfer speeds. Dropbear is capable of port forwarding and X11 forwarding, making it a suitable replacement for the OpenSSH server in some cases. It is available for Unix-like systems and Windows, and is the default SSH server for many Linux distributions.
Discontinued Not updated as of January 23, 2013.
OpenSSH
OpenSSH for Windows
NetCrypt
Discontinued The project seems to be no longer updated. The latest version, 5.3 rev2, released in February 2010, can still be downloaded from SourceForge.