Plugable is a company that talked in depth about support for
Windows 8 RT USB devices, unfortunately it doesn't seem like any of their USB network cards currently work. You can certainly try other USB network devices, if it installs in Windows 8 Pro without a driver it will probably install on Windows 8 RT just fine.
There's been quite a bit of back-and-forth on Windows 8 RT support for USB Ethernet adapters. Turns out that there
was a driver for one of the Plugable adapters, and a bunch of people started using it. So Plugable wrote up installation instructions and posted them along with the driver. It seemed to work well, and everyone was happy. Or so we thought.
Recently, Plugable received a letter asking us to stop distributing the driver. We're going to do that, but plan to keep the WinRT drivers up for a bit longer, so that people who just bought an adapter through Amazon (and used the "Super Saver Shipping"
option) won't be disappointed when their package arrives "5-8 business days" from now.
We hope that this issue can be resolved soon, and that this and other new USB devices can work with Microsoft Surface (and other Windows RT tablets).
For more information, see http://plugable.com/2012/12/11/windows-rt-surface-usb-ethernet-takedown
Jonathan from Plugable