From Hamsterworks Wiki!
I've been playing with Jack Gassett's port of the AVR to his Papilio One FPGA based Arduino board - the one on OpenCores build is built around the Altera FPGAs
I wrote this small tutorial on how to get your program into the AVR8 Memory.
I've also put a text mode video output alongside my AVR8 processor.
Differences from the real thing
On the original AVR103 had one input only port an done output only port (alongside it's four bidirectional ports). Because of this there are two 'undocumented' data direction registers the need to be set appropriately.
Of course these are not defined in the header file so you will need to add your own.