Hi all...
Just thought I'd post a quick update from my wiz810mj module hacking...
I've just in the last half hour or so successfully uploaded a sketch to a Bare Bones Freeduino (thanks uCHobby!) via an ethernet connection using a Diecimila as a network/serial proxy.
So, by executing a command like this:
arduino-0010/hardware/tools/avr/bin/avrdude -C
arduino-0010/hardware/tools/avr/etc/avrdude.conf -pm168 -cstk500v1
-Pnet: 192.168.2.105:7 -D -v -v -v -v
-Uflash:w:/tmp/build40791.tmp /Blink_edit.hex:i
causes avrdude to connect to the wiznet module attached to the Diecimila and communicate with the "programmer" which is actually the BB board connected to the Dieci's serial rx/tx pins. The Dieci sends the network input to its serial output and returns the serial input to the network output.
At the moment it's a mess of alligator clips, component leads and breadboard but it works--I've got the flashing LED to prove it! 
The code's not in SVN yet but it's trivial to adapt one of my earlier examples if you can't wait. 
The code, which is unoptimised and has heaps of unnecessary functionality (for this task) compiles to about a 9.9k binary--so I think it might be able to fit into na atmega8 with a bit of work.
Anyway, thought someone might be interested. But for now, it's early and I need to go get some sleep...
--Phil.