As someone who spends a fair bit of time on the road, I've become increasingly paranoid about my backup strategy as well as my general "travel kit". To address both, I made a purchase recently that I'm so in love with I just had to blog it:
The G-Drive Mini from G-Tech is an awesome little portable hard-drive. I got the 250GB, dual interface model and so far it has been wonderful. At 250gb, it has plenty of room to store my Time Machine backups as well as any extra files I (might) need on the road.
It's a really nice looking little unit: aluminum case (that matches my macbook pro), with it's own heat sink. It's quiet enough that I hardly notice it. AND it comes with it's very own leather carrying case.
I'm happy with the new addition to my travel bag, and I'd recommend it for yours as well.