EtherCAT is probably the most advanced industrial Ethernet bus out there.
Since it's specification is public to the members of the EtherCAT Technology Group, anyone can implement an EtherCAT Master.
On the other side, EtherCAT slaves have to use an ASIC chip. One of these chips is the LAN9252 from Microchip, which is used in the Arduino Shield EasyCAT by AB&T. With this shield you are enabled to build custom EtherCAT slaves with astonishing high speed data transfers on a simple Arduino board.