SSH Secure Shell

Windows (Putty)

putty.exe from Putty-CAC, an improved version of Putty-SC adds PKCS#11 support to putty, which the upstream version does not have. It works flawlessly with OpenSC PKCS#11 module. A fork of Putty, named KiTTY also exists. Using the pageant.exe from Putty-CAC allows to use WinSCP with smart cards as well.

Linux / Mac OS X (OpenSSH)

See OpenSSH and smart cards PKCS#11 for more information.

PuttyCard (deprecated)

PuTTYcard is another, independent implementation to add smart card support to putty. Read more about it here.