for HDD...you can bubble-wrap or wrap among ur clothes...quite safe..
one of my friends thought that it would be safe, he did exactly that, and his luggage was a hard-shell samsonite. it was 5 days old, when he took it out in his residence, it made r2-d2 noises.
died the next week.
haha....if not, u buy ruggeized hard disk from Lacie lor, i'm using that now and I travel about twice a month, no problem so far...never even bubble wrap.
I'd not bring the tripod if I were you. And even if you are, I suggest you to check online if that country has any restrictions of using tripods in public. I heard that Italy restricts the use of tripods and medium-format cameras without a permit, so that people won't do commercial stuff for the Italian tourist attractions and stuff [i assume].
-Charger with the appropriate converter.
-The most versatile lens in your arsenal. Don't bring prime lenses, or super-zoom lenses unless you know what you are doing. If the kit lens is all you have, then perfect.
-A nice bag. Preferably sling, so you can access your bag easily, and people cannot secretly open your bag while it's behind you [ref. to backpacks]
-2 to 3 Memory cards, Total can be anywhere from 4 to 16 GB, depending on whether you shoot JPEG or RAW, and the resolution. If RAW, get 8GB min. needless to say for JPEG.
-A Hard Drive. Why 2 cards even with a hard drive? Well, simple. while one transfers, you can still shoot with the other. remember to delete / format the card after transfer, though.
About the hard drive, Please take good care of it. I 'killed' my Sony HDPS-M10 while I was traveling in Italy last year It probably didn't enjoy spinning a hard drive while on a bus.