SymbianTutorial.org is a good website to learn about fundamental application development in Symbian (especially series60).

Though some information about the IDE is slightly outdated (as stated on the website), the tutorial website covers basic Symbian data type, class naming convention, exception handling, input/output, gui handling basics and how to create resource file for Symbian development platform.

The website itself is structred in a way to introduce reader to Symbian application development environment, which is the main platform used in Nokia and Sony-Ericsson smartphones.