The primary sites for Symbian development infomation are:
- Forum Nokia
- Symbian Developer Network
- Symbian Developer Monthly Newsletters aka SCN
- Symbian Signed - the necessary evil
- Samsung's Mobile Innovator - S60 developer site
Cyke's S60 Python package selector is great if you don't know which version of Python to get for your phone. This page tells you which phone uses which edition of S60, and which feature pack it has.
Projects for other languages are also catered for on the Symbian OS.