I have an Archos 80 G9 that I picked up at a local Staples for $199. I think they are now running about $149.
The 80 G9 has a port on the back that is meant for a USB 3G adapter. When you turn on the 3G port in the setup, you can pretty much connect anything to it. I have a 32GB thumb drive socketed into mine right now that I use to hold videos. I have also plugged in my 250 GB external hard drive that is powered through the USB port and it is accessible and I run various videos off of it, also.
The only thing I can say is a downside on this is that the port is recessed in the tablet and a thicker usb connector may not plug into it correctly. The flatter the connector, casing, and/or cable the better it will plug in.