I was brought to look into my sources for NetBSD network
boot ROMs again (to implement support for PCNET-PCI).
After some (but not enough) cleanup, I made the current
state available at:
zelof1.zel.kfa-juelich.de:/pub/NetBSD/bootcode-300996.tar.gz

Besides PCNET-PCI support (which could be easily extended
for any LANCE-based card), there are some other
improvements over the last snapshot:
-rudimentary bootmenu (based on getsubopt(3))
-bootfiles can be gzip'ed
-can be installed as hd / fd bootsector (uses a fragment list
 like other platforms)
-serial console autodetection

best regards
Matthias Drochner