Unix

FISH
A free SSH client. [VMS]
http://www.free.lp.se/fish/

FSH -- Fast SSH remote command execution
FSH is an extension to ssh (on UNIX only) that permits sending multiple commands to the remote host through one SSH tunnel.
http://www.lysator.liu.se/fsh/

OpenSSH
Freely available SSH1 and SSH2 implementation. Designed as part of the OpenBSD project, but portable to a number of unix-like operating systems.
http://www.openssh.org/

Psst
An open source SSH client is available for download, as well as general SSH documentation and links to other secure communications projects. [UNIX]
http://www.lysator.liu.se/~nisse/lsh/