This is a very common task for photographers and, because I seldom fire up my computer these days, I have been looking for a way to do this with the iPad. I have finally found a convenient way to do it.
I have a Western Digital NAS (MWBE) which has a USB port and has an option to expose the embedded Linux shell.
I plug the SD card into a mini SD card reader and plug that in the USB port on the NAS.
I use iSSH to establish a shell session with the NAS on the iPad and copy the files from the SD card to a destination directory. I like to copy jpg and raw (cr2) files to separate subdirectories so that adds a few extra steps.
To save typing (and typos ), I use a Numbers spreadsheet to construct the necessary Linux commands. It is a simple matter to copy them from Numbers and paste them into iSSH. I could use the vi editor on the NAS to create a script but I think that copy/paste from Numbers is actually easier.
I thought that other photographers might be interested.
This is a typical sequence of commands (copied from Numbers):-
cp /shares/usb1-1share1/dcim/102canon/*.jpg /DataVolume/Download/Photos/20110426_Test/jpg
cp /shares/usb1-1share1/dcim/102canon/*.cr2 /DataVolume/Download/Photos/20110426_Test/raw