I carry a 60GB portable harddrive and two 8GB thumbdrives when I travel. The WesternDigital Passport drives are great and if taken care of they will last.
The thumbdrives that are best are the ones that use a rubber seal around them to secure it. This makes them waterproof and rugged. I've washed one of mine before and it came out fine.
Something else I do is a backup to Amazon's S3. I encrypt everything and throw a copy up on S3. It's pretty cheap, costs me around $3 a month.