The easy-to-use Qt Application and UI framework not only simplifies C++ development but quickly deploys apps to multiple mobile platforms without rewriting source code.
Getting started guide is here
The latest Qt 4.6 brings full Symbian and Maemo support. In addition, there are a set of Qt API’s that offer key mobile platform features such as messaging, location, contacts are currently available but are labelled as Beta.
Visit the Forum Nokia wiki for tips and tricks (oh, and if you think of some add them there as well 😉 )
If you get stuck, there are always the Forum Nokia Discussion Boards for Qt.