It certainly would be great to get Ethernet on the Arduino board, but it is probably a little much for the ATMega to do all the TCP/IP/DHCP stuff.
I suggest looking at combining a serial-to-Ethernet ASIC based system like:
WizNet:
http://www.saelig.com/miva/merchant.mvc?Screen=PROD&Product_Code=ETH004&Category_Code=ETH
or what I've used, the Xport which is very solid and easy to use:
or the cheaper Xport Direct: