If you have a Symbian series 60 phone, you *must* be having these freeware apps.

Opera
The popular Opera web browser. The latest version is 8.5
http://www.opera.com/products/mobile/products/?os=series60

Fexplorer
File manager (like Windows explorer). Its the most popular one and its my favorite. Has advanced features like edit/preview/cut/copy/paste..
http://www.gosymbian.com

Bemused
An app that allows you to control various PC applications via bluetooth. Supports Winamp, Windows Media player and powerpoint. (I am not sure whether the latest versions of these apps are supported)
http://bemused.sourceforge.net

Forward
Foward is a simple program that allows you to forwward on (by bluetooth, MMS etc.) that have been received via bluetooth, MMS, infrared etc and are in the Inbox. It also allows you to save files in the inbox elsewhere on the phone
http://www.compsoc.man.ac.uk/~ashley/

Real Player
The most popular mobile audio/video player. It comes preinstalled on most of the Series 60 phones
http://symbian.helixcommunity.org

Task Spy
A task manager similar to the Windows task manger
http://www.pushl.com/taskspy

Calcium
An advanced calculater with a nice set of features
http://mtvoid.com