Currently available 'official' Ethernet shields ( http://www.smartprj.com/catalog/index.php?main_page=product_info&cPath=1&products_id=58) are described as 'PoE ready'. I know what PoE stands for :) but what that means for Arduino w/ shield? I don't have any PoE power injector nor PoE enabled switch so can not test these new shields.
Shield description seems to be not updated on wiki yet (http://arduino.cc/en/Main/ArduinoEthernetShield), so I'm just curious what that 'ready' means? Arduino board need some change to be powered via PoE? Or ?
Have you asked the people that sell the board? It could be that four of the eight RJ45 connector are available to run power over, and the other four connectors are used for a 10baseT ethernet connection.
but what that means for Arduino w/ shield?
Given what appears to be a big regulator, and the heatsink area on the board, I'd say there's about a 97% chance that it means that the board will generate 5V to power the Arduino from the PoE voltage. However, also given the size of the heatsink area, I'd say you probably shouldn't inject more than 12V into the Ethernet. Especially if you have another shield, or other support electronics, being powered from it. Personally, I would've preferred a standard screw-on heatsink, instead of relying on a piece of the PCB.
I don't have any PoE power injector nor PoE enabled switch so can not test these new shields.
Well, you can't test the PoE, but the board should also be able to work in a normal configuration, with the Arduino providing the regulated 5V. But "should" doesn't always wind up being "does", so you need to ask the seller.