Since you've got LocalTalk running to the box, then
I'd also run MacGate
which would let you run MacIP (IP over LocalTalk).
Good page for MacGate looks like
http://www.linux-sna.org/software2/Appletalk/index.html
As for other fun topologies, you already mentioned
TokenRing. My personal
choice would be to also add HomePNA (Ethernet over phonelines). The 1MB
HomePNA 1.0 cards (the only ones supported by Linux)are very cheap these
days. I picked up a pair from Computer Geeks (
http://www.compgeeks.com) for
something like $12. Now if I could just find a cheap Ethernet/HomePNA bridge
for the Nubus Mac in the spare bedroom...
I was lucky and picked up a couple cards from MicroCenter including the
network/modem gateway card.