Finally I got a shark (thanks a lot, Stephen!) and got it booting
from FreeBSD. That was a little bit tricky, here my summary just
for the record.

There is a "Diskless NetBSD HOW-TO" at 
http://www.netbsd.org/Documentation/network/netboot/

The shark document is "coming soon", maybe this will help a little
bit.

In http://www.netbsd.org/Documentation/network/netboot/nfs.html
is mentioned to mknod the console with 0 0. This is not true for
the shark, which needs 2 0.

I'm not a NFS guru by far, but it seems, that FreeBSD and NetBSD
have different ideas about NFS V3. So you need to tell FreeBSD's
mountd to only speak V2. The above mentioned page tells you to
use the -r flag for mountd, actually you need -2r.

And the biggest headache. Whenever the shark ordered a bigger file
via NFS, the FreeBSD sent it fragmented, of course. The first file
was /sbin/init, which results in one NFS answer and 5 following 
fragmented UDP packets. The shark was not able to receive them in
time and asked again and again. The answer to this problem can be
found here: http://www.freebsd.org/handbook/nfs.html, directly on
"Problems integrating with other systems". You just have to tell
NetBSD to mount the remote filesystems with -r=1024. So it should
look like this: fastws:/sharedfs /project nfs rw,-r=1024 0 0

So, now I have to find out, how to configure X and how to get a
german keyboard layout for the console.
Someone wants to port wscons to the shark? :-)

-- 
Tom