network card to pic interfacing
There are several projects at the web. Some years ago I have experimented with a NE2000 compatible NIC and a pic16f877.
This NIC is based on a Realtek 8019AS. I remember that I had to try several cards to find one that worked with no problems.
There is an evaluation board at microchip with a similar configuration.
Also check:
**broken link removed**
Others have used Atmel microcontrollers or 8051.
There are commercial boards using a microcontroller and a 8019(or similar) chip.
You can use an old ISA card wired to a board or you can build a card with the ethernet controller, PIC and the 10baseT interface components, included.
As you see it is possible and it has been done.