This is a Microchip ENC28J60 Ethernet module I purchased online. It uses an SPI interface and has 5V level conversion included and is a perfect candidate for a 65SPI peripheral.
I am using this on my SBC-3 with custom drivers and Adam Dunkel's uIP Stack. Applications include a Web Server (with files served from the FAT16 IDE interface), Telnet Server, and SMTP MSG sender. The uIP and applications are compiled using the CC65 C compiler targeted to the SBC-3.
The firmware sources are located here -> enceth.zip