I'd recommend putting some shine on the following application, I think these would make the NIT a very mainstream device.

USBtoVGA - This is something I think Nokia can greatly contribute to. Of course a hardware Video Out would work also.
Abiword - This project just need a bit more porting support to make it stable and generally screen clean-up work so it's useable for the general public.
Gnuermic - Stable & very useful, but some secondary screen need to be cleaned up
"Powerpoint" compatible application - This combine with the USBtoVGA would make the NIT the default hardware for every traveling salesman / presenter.
Contacts w/ built in syncing - Many good application to build upon, but most need some cleanup or better sync, importing, etc.
Calander - Many good application to build upon, but most need some cleanup or better sync, importing, etc.
Phonelink - A great application (assuming a better base contacts application) if the next generation NIT doesn't have built in phone, but seems to suffer from installation / setup challenges

Just my two cents