I keep my Compact Flash cards in a cheap metal case I bought online for around $10, which you can still find them on eBay pretty easily. My main Compact Flash (256MB SanDisk) card stays in my x51v all the time. So far I haven't noticed a problems with the card reading/writing. I did just purchase a Seagate 8GB microdrive from Amazon.com; hopefully that won't give me any problems either.
InAnyCase.com has some really great cases for Compact Flash and Secure Digital. Two flash card cases I been thinking of getting from them include their UFP Plus Multiple Format Media Case (
photo) and CardCaboodle (
Photo 1 &
photo 2).
This is the CF case I use...
I also own one of those flash card to USB thumb drives. I bought one for my Sony camera. I think the brand is called MediaGear XtraDrive. It's a real cheap little thing. Works fine as a bulky thumb drive, but its a paint to install & remove the card.