I use an Archos 605 as my back-up on holiday
http://www.amazon.co.uk/gp/product/...&pf_rd_t=101&pf_rd_p=467128473&pf_rd_i=468294 This can also be your entertainment as well, as it can act as an MP3 and video player. You would need the extra battery dock to back up from your camera though
http://www.amazon.co.uk/Archos-Batt...1?ie=UTF8&s=electronics&qid=1261993610&sr=1-1 and this would mean you could also charge it from the mains whilst travelling and play your videos on to a TV.
I bought one as a birthday present for my girlfriend last year, and was so impressed with what it did and how it could also be used as a photo viewer, that I bought one for myself.
I do only use it for back-up on holiday though, and still keep all the photos on my memory card until I get home. For such a big trip, I would suggest not deleting the photos from your card and also backing them up to an external device.