It’s well known how expensive SxS cards are for the EX series of video cameras and filmmakers quickly found ways to get cheaper storage. The most widely accepted way to do this was to get an expresscard adapter, such as the MxM adapter, and use SDHC cards. This is what I have in my EX3: the SxS card that came with the camera and 2x MxM adapters, with one 16gb SDHC and one 32gb SDHC. Those are the dedicated cards, but as we have several SDHC cards, we can just swap them out of the adapters where needed.
But now you can also get adapters where, instead of having an SDHC slot, you have a USB 2.0 port. This means you can plug in external hard drives or flash drives and store increasing amounts of media. These cards are similarly priced, see this MxM USB 2.0 adapter, but now cards are being made available at much more reasonable prices. Take, for instance ,this USB 2.0 expresscard for £5.03.
See the video below for this set-up in action (it’s not in English, but you get the picture):
He also has a video for an 8gb Sandisk Cruzer flash drive.