As far as I know, you have to jailbreak to do this.
The camera kit comes with 2 connectors - SD and USB. The USB connector won't read any of my flash drives on my jailbroken ipad due to the power requirements, although some people report success with low power, low capacity drives.
You can't use the SD connector on an unjailbroken i-device for anything but viewing thumbnails of the photos on it and transferring all or selected ones to the device.
After jailbreaking, if you install an app called iFile (costs money but has a free trial) you have full access to the file system on the device and you can use the SD connector to view most any kind of files and transfer them back and forth. You can also view photos on the SD card full-screen. For iFile info see here:
iFile
For features and file types, see here:
iPhone Applications and Tips - Feature Requests
iFile also has a server in it that you can use to transfer files wirelessly from your computer.
If you do this, be careful when in the file system. If you mess something up it could mean trouble. I would liken it to going into the registry in Windows.
There is also a free app out there called iPhone Explorer that I think you can use to transfer files, but it's not added storage like an SD card and you have to be connected to a computer to use it.