I recently upgraded my Vodafone contract to the excellent Nokia E65, which is the best mobile device I have used (great form factor, fast CPU, Built in WLAN and Symbian OS 60.3 is excellent!).
One application that I recently discovered was Putty for Symbian OS, this fantastic little app allows me to connect to my remote linux servers from both WLAN and GPRS connections – sure, you’re not going to be doing any application development with it, but it’s great for rebooting a server or doing remote diagnostics (or just showing off to friends!)