The popular PuTTy application for Windows, which allows administrators to connect to Unix or Linux hosts at the command line, has been ported to the Symbian Series 60 platform.
It is available for download from the SourceForge web site here: http://s2putty.sourceforge.net/download.html [1]
It did not require any additional pre-requisite components to run on my Nokia E71. Simply copy the SIS file to the handset and run it, once installed it will be listed in the Installations folder:

Launch the application, and edit the Default profile that will be listed:

The following options will be available:

Under the General options you can define the hostname or IP address to connect to as well as the user to connect as:

Under the SSH options you can specify the port to connect using as well as the protocol version:

When connecting to the server for the first time you will be prompted to save the server's RSA key in the list of authorized hosts within the Symbian operating system:

You will then be prompted for the password of the user account you used to connect with:

You will then be connected to your remote server.
Links:
[1] http://s2putty.sourceforge.net/download.html
[2] http://ukblog.im-mobility.com/category/blog/e-series
[3] http://ukblog.im-mobility.com/category/blog/n-series-0
[4] http://ukblog.im-mobility.com/category/blog/open-source
[5] http://ukblog.im-mobility.com/category/blog/putty
[6] http://ukblog.im-mobility.com/category/blog/ssh
[7] http://ukblog.im-mobility.com/category/blog/symbian