Tested the Ethernet Pro shield yesterday. Found that the MAC address can be changed by user. Tested the sample programs for the static and dynamic IP addresses. The DHCP in following can compiled under the Arduino 0.23 and not 1.0 (some renaming the header files are needed - haven't try this).
http://blog.jordanterrell.com/post/Arduino-DHCP-Library-Version-04.aspx
