Can anyone recommend good simulation software for mobile devices? I am most interested in Nokia smart phones.
You are right! The Nokia phones runs on Symbian Platform.
There are quite some variants out there, But S60 is better. UIQ is not doing that well lately.
Have a read at Developing with S60
You can download the SDK from forum.nokia.com. So the Emulator comes with the Developer Kit. You can try to build and run the samples on Emulator to get first hand feeling.
Unfortunately Developing for Symbian is not walk-in-the-park. You can get some developer feelings here:
Alternatively you can look for Windows Mobile. Which has pretty easy learning curve if you have prior knowledge in any of the areas [Win32, or MFC or .NET C#]
Getting Started with Windows Mobile
or If you are comfortable with Java, check out J2ME. It has a wireless toolkit with decent emulator.