where I found some information

Microchip manufacturer of the PIC microcontroller: datasheets, etc.
Realtek manufacturer of the NIC: datasheets, etc. (search for 8019AS)
National Semiconductor manufacturer of the 8390 NIC (original NE-2000?). Very good datasheet (search for 8390).
Atmel manufacturer of the onboard EEPROM (search for AT93C46) some PIC information
GPASM my current PIC assembler of choice; for LINUX as well as for Windows. GPASM is a replacement for the Microchip (TM) MPASM assembler, distributed under the terms of the GPL. Included in the gputils package
Ethereal great piece of software for analysing all that packets on your network great resource for various documentation, RFCs, etc.
TCP/IP more than just a few links for TCP/IP and other network related information
ISA bus "what is where" and "what has to happen when" on the ISA bus
Web51 a GPL Project for Embedded Ethernet Applications (tons of implemented protocols!)