I extended the relay controller design that I put up recently to do the task of being a watering system. Getting the code to fit into an AtMega328 was a bit tricky, I kept having stack overflow problems because my strings were too big. But it fits!
And it uses a Microchip ENC28J60 ethernet controller.
Full design files are in the Instructables.com article here.
If you want to download the project tree – Here it is.