Take a look at www.iinchip.com

I am using the IIM7010 module to connect my AVR microcontroller. It has a very easy to use socket interface, with which you can connect with up to 4 internet nodes. You can either be a server or a client for each socket independently.

They even have lots of sample code, as well as C libraries for using it right away. Nice Address/Data bus connection, requires an external memory address range of 32Kbytes (all Rx-Tx memory on chip).