With full SSH support for Symbian OS devices, PuTTY makes it easy to adminster almost any Unix-based server. PuTTY looks and acts like a classic SSH terminal, allowing users to establish a secure connection right from their mobile phones. It supports versions 1 and 2 of the SSH protocol, but not Telnet or other protocols. It also supports key authentication, though you'll need to generate keys with the PuTTYgen utility, freely distributed with the PuTTY for Windows platform. The clean, clear interface looks pretty good--certainly good enough for terminal software. On Series 60-based phones, you can even choose fonts and reverse the background colors. Good performance, decent looks, and a free price tags? For programmers and sysadmins with Symbian phones, PuTTY's a no-brainer.
This software is SO easy to install and use. I've never ever had any problems installing or using it. Plus, its memory footprint is very lightweight, so you can start it up in a jiffy (think production issues which require immediate resolution)