Adafruit Ethernet Shield
I assembled and soldered it myself. The power connections are certainly working, as it gets a DHCP address and responds to pings when connected. Now to write some test code.
(photographic side note: I was quite surprised at how well this picture came out. It was taken using an N95 in closeup mode, on a white piece of paper, with a power-saving lightbulb in an anglepoise lamp overhead. I sent it to Flickr directly from the phone and brought up the brightness and contrast using Flickr's online editing. lofi all the way.)