Putty is an open source SSH and Telnet client software and terminal emulator works on Win32 and Unix platforms. You can download Putty, here www.putty.org
SecureCRT is a commercial SSH and Telnet client software and terminal emulator works on Windows, Mac OS X and Linux platforms. You can download SecureCRT, here www.vandyke.com
OpenSSH is a FREE version of the SSH connectivity tools. It uses encrytions to encrypt all traffic.You can download Open SSH, here www.openssh.com
KiTTY is a fork from version 0.62 of PuTTY, that works only on Microsoft Windows platforms. Beside the original software, KiTTY has additioanl features. You can download KiTTY, here kitty.9bis.net
Terminals is a secure, multi tab terminal services/remote desktop client that uses Terminal Services ActiveX Client. You can download Terminals, here www.terminals.codeplex.com