This page points you to online resources to get you started in developing apps for the Symbian S60 environment. Note that you can also develo using J2ME, although you will be limited in being able to interface deeply itno the OS.
S60 App or Python Script?
Nokia has release a python for S60 meaning that you can easilly and quily develop highly capable apps for the S60 platform. As always- there are plusses and minuses to this- i.e. ease and speed of develpment versus limitations in deep OS integration and application speed.
Python for S60
Nokia's Opensource Python for S60 Wiki- a great place to start and read about the the cabailities available.
Panjak Nathani's excellent Python for S60 Site - great starting place for installation and code tutorials