Arduino compatible with PoE
From the same post on Reddit as the other one I found out about these IBoard Arduino compatibles. They were the same price as the previous two that I got, $29, but these are a little bigger and have more built-ins. In addition to the Ethernet port and XBee ports, they also include a MicroSD slot.
These boards are about the same size as a real Arduino, a little larger than the XBoard. They are 3.3v based which I'm not sure yet how difficult will be to work with. They also have used up all the digital I/O pins internally, the only thing you have access to are the analog pins.
The manufacturer says that they also support Power over Ethernet (PoE), however I don't believe it is true 48V 802.3af PoE. I think it only supports up to 24 volts coming down the unused pairs. The schematic shows that just pins 7 and 8 on the RJ45 are used for power. It looks like there is a built-in bridge rectifier on those two pins so polarity isn't an issue. I'm also not sure how much the onboard regulator will like getting 24V for extended periods.
Being able to send power down the ethernet cable though is very exciting. It's very easy to fish an ethernet cable to wherever I need. Plus the bonus of not needing to have two wires running into the project will be nice.