We have seen one in the last two days and here is another USB Drive to NAS device called Pogoplug from CloudEngines. Pogoplug has a dimension of a large AC adapter, unlike Hitachi SimpleNet, it has a single Ethernet port and only one USB port provided.
Once this CloudEngines Pogoplug connected to your network, your PC will recognize it as a drive and will appear in your list in Windows XP or Vista. You can navigate through the content with the help of a built-in web browser, or via the specially designed free client apps for accessing Pogoplug directly via your OS.
There has been a complete review on this cool USB-drives to NAS device at HotHardware, you can find the detail about this Pogoplug including the benchmarking of this device.