Forum Nokia has some documentation about the Nokia 9500 and Series 80 in addition to the SDKs and emulators. The Series 80 UI Style Guide is designed for programmers, but sheds quite a bit of light on the inner workings on the newly revamed Series 80. There is quite a bit of information about how native apps behave.
There is also an IPv6 guide for hardcore Symbian C++ programmers.
The most up to date information can be found at the Forum Nokia Series 80 page. If you have not already, check out my Nokia 9500 roundup and my look at the Nokia 9500 emulator.