The IBM Website lots of documentation on the NC, most of it can be found in PDF format.
The latest updates can be found at http://www.as4000.ibm.com/networkstation/rs6000/ including
Or from http://www.ibm.com/nc/pubs/
There is a mailing list available called The NetVista thin Client Linux Forum it can be found on http://techconnect.ease.lsoft.com/archives/netvista_thin_client_forum/network.htm , the archives can also be found there.
There are a lot of new resources online about Linux on the PPC40X. Here is a small list of them. http://www.borg.umn.edu/~grant/Linux/ it seems like some of the Netstations contain a 403GC[X] on this page you can find a Linux kernel for that PPC. If anybody succeeds please contacte me ! http://www.mvista.com/products/405gp_status/main.html Montavista Software is doing a nice job in porting the Linux kernel to the IBM PowerPC 405GP based Walnut System:
More recently we established a Wiki to discuss the development of Linux on the Netstation, you can find it on http://howto.ipng.be/NetstationWiki/ The effort actually worked out and there is a totally new project on SourceForge where you can download the required software to boot Linux on an IBM NC 1000. http://sourceforge.net/projects/networkstation/