What is a good microcontroller for Ethernet applications?
Microchip's PIC18s with built-in ethernet are excellent for this, just add a magjack (or other connector with built in magnetics) and download their TCP/IP stack. You'll be pinging things in no time. For more grunt, the PIC24 and PIC32 also have TCP/IP stacks designed to run with one of the SPI Ethernet MAC/PHY parts they offer (ENC624J600 or ENC628J60).

ST also recently enhanced their ARM Cortex based STM32 line to include on-chip ethernet, but you'll need an external PHY and magnetics. It's an option if you're already looking at the PIC32.