I'm also looking for a new alternate backup solution at the moment. In the past I've used the CompactDrive PD70X - I went for this because it was a standalone device so I didn't need my laptop to be able to back up onto it, much like the Epson etc (although it's a lot more basic). It also ran on AA batteries, which I've always got with me for strobes etc. My worry with using standard external drives or DVD's was that if my laptop went down, I'd be stuffed: a real single point of failure.
However the Compact drive was not without it's problems: several times I corrupted the File Allocation table and had to reformat the drive (for which of course I needed my laptop). Most of these problems were to do with using batteries rather the power adapter, but the bottom line was that the device was not as reliable as I needed it to be: Certainly not enough to be a completely redundant solution if my laptop died on a trip.
I'm currently looking at the archos 5 http://www.archos.com/
With this device you can read directly off the camera via USB (providing you have the optional adapter). It displays JPEGS but being a multi function device it also plays movies and music (the screen is sweet, I used a friends earlier model a few weeks back). Admittedly these abilities are not a prime consideration, but damn handy when your laptop battery packs up 3 hours into a 12 hour flight.....
Anybody had any experience with these? Reviews on the net seem generally positive, although it certainly has a few niggles.
cheers
Steve