Updated document "Symbian OS: Designing Bluetooth Applications In C++ v1.1" provides developers having already existing knowledge of the Bluetooth technology with enough information to develop Bluetooth applications in C++ for the Series 60 and Series 80 Developer Platforms and for the Nokia 7710 using Symbian OS Bluetooth APIs.
This article describe how Symbian OS Bluetooth APIs give applications access to RFCOMM, L2CAP, SDP, and HCI.
This is pdf document, size 709.0 KB, direct link here.
Forum Nokia also have some good examples about using Bluetooth on Symbian. Another good example can be found in the sources to the book "Developing Series 60 Applications" available from here.