ENC28J60 Ethernet LAN / Network Module

http://dx.com/p/enc28j60-ethernet-lan-network-module-for-51-avr-stm32-lpc-150604

Source code & Libraries

Library for ENC28J60 Ethernet LAN : EtherCard
Simply download ethercard folder and put it on path-to-your-arduino-folder/libraries/<EtherCard Folder>
Many examples are available in the folder ethercard/examples

Another library is available to allow an Arduino Card to use MQTT : MQTT for Arduino with EtherCard library
There are some examples available in the folder NanodeMQTT/examples To add this library, proceed as previously. Don't forget to read the Readme.md file.

STM32

http://blog.tkjelectronics.dk/2012/08/ethernet-on-stm32f4discovery-using-external-phy/ ??????