The answer is the Digimate. (Sadly they are not paying me to say this.)
It's basically an external hard-drive, with built-in slots for memory cards: CompactFlash, SD, MemoryStick, MMC, MD, SM, XD, whatever. (I use CompactFlash.)
Stick in your memory card, switch on the Digimate, press the copy button, and the contents of the memory card are copied to the Digimate's hard drive.
My CF cards are 256 MB, and it takes perhaps 3 or 4 minutes to back one up.
The Digimate attaches to your computer via USB 2.0, and shows up like a regular external hard drive.
It's dead dinky. And, so far, so robust - it's done 10,000 km in my panniers and doesn't seem to mind. I do wrap it up in a few old socks, to protect it from the worst of the crashes.
You can whack in basically any hard drive. Mine has a 60 GB job, and cost, if I remember rightly, around 800 RMB, including the hard disk, in Shanghai last year. That's around US$100.
Where can you get a Digimate? I don't know. I haven't seen them on Amazon. Try the big electronics mall at the back of the big glass globe shopping centre in Xujiahui, Shanghai. That's where I got mine.