I have done some work on programming Symbian Devices, in particular the Sony Ericsson P800. As this project continues I will put further information and resources on this page.
The first result of this project is a getting started guide to Symbian devices. This covers installing the SDK and compiling an application using GCC.
I have used GCC in this document since it comes with the SDK and allows a developer to compile and deploy applications without having to download or purchase any other software. I hope it will provide some useful advice and help you avoid some gotchas developing for this platform.