Hope you don't mind me adding to this, Jamie!! :D
What should I pack???
Okay, everyone wants to know this. Each of us has our own personal list, but as a general rule, here's a good way to go:
First Aid Kit.
I always pack a heavy duty hiker's First Aid kit. I carry an Atwater-Carey Backpacker kit. Has everything i need for a good day's hike (moleskin is your friend.) I've augmented it with a few necesities: A few condoms, (they make great finger cots, as well), compact sewing kit, copies of my passport, driver's license, and ISIC card, and ICE contact info. First Aid Kit: A-C First Aid Kits
Not to be confused with the First Aid kit, this has all the shaving kit, deoderant, toothbrushes, contacts backups, some bandaids, antacids, meds, etc. This stays in the bag in the room, but the small first aid kit goes with me. This is your typical traveler kit. Mine's an Eagle Creek Wallaby II, available just about anywhere.
For the obvious, as well as the fact that it makes a great tarp if the ground is muddy. One for me and a cheapo vinyl one for my bag if necessary.
They never go bad, and if you're hiking/walking all day, heavy in nutrition. These sort of things are the little stuff nobody remembers.
Good for lashing things to my pack, as well as the obvious.
MSR Pack Towel:
Dries fast, compresses well, and doesn't take up as much room as a full-size bath or beach towel. Remember, be a hoopy frood. Know where your towel is. MSR: Packtowl
Batteries for Camera, iPod, MP3, etc:
Because the things will die at the worst possible moment.
I like Rough Guides. Some folks will advocate only taking the pages of stuff you want to see ahead of time, stapled together. I don't like this idea, as I'm prone to changing direction once there with the wind.
Keep the time, jot down your thoughts. You'll thank me later.
Duh. Keychain variety.
Leatherman or Gerber tools are far more versatile than the traditional Swiss Army Knife. The pliers alone are worth it. Gerber Compact Sport Tool here: Gerbergear.com
Take a roll, make a loop about 10 cm long, and start wrapping it around until you are confident you have enough (about 30-40 layers). This stuff saves lives. There are "backpacker" rolls made that are overpriced flat rolls without the cardboard core. Waste of money. The stuff costs less than a dollar or two at your local hardware store.
Never know when you may need to take a shit. Seriously. Granted, this stays with the main pack, but its an honorable mention
A good hat.
I have a Seattle Sombrero from Outdoor Research. You can get them here: REI
I have a book I always travel with, Hunter S. Thompson's The Rum Diary
. Also brought Zen and the Art of Motorcycle Maintenance
I tend to get a lot of reading done on the buses/planes in between. Plus, the quiet solace of a good book on a beach can't be beat. Pick two. Bring 'em. But bring the paperback versions!
Digital camera with batteries and biggest memory card you can afford.
Smaller is better for the packer on the weight savings. A Nikon SLR digital rig is a lot to carry around and a beacon to would be thieves. I have a Nikon Coolpix 5600, and a nice little pack that clips to my belt. Its unassuming, and though it won't make me the next Ansel Adams, it takes decent pics. It would suck if you didn't have pics to remember the friends you made. A good add-on is a cheap disposable 35mm cam with a flash. You never know
Small compressable sleeping bag:
Good idea, since you may need an extra blanket, and as Jamie said, you never know.
Again, things may vary person to person, but generally, the above are universal.
Padlock, combination style, and bike cable lock. Cable locks are great for lashing your pack to a bed, etc. Padlock for the locker you may find on your way.
Under-the-shirt-style money belt. I have an Eagle Creek I like, it keeps my passport and backup cash, etc together. Great for the traveling- NEVER KEEP YOUR STUFF IN YOUR PACK!!! Seen too many folks lose their bags at a bus stop, etc, and their papers, money, etc. are in the pack. Too dangerous!
Zip-style moneybelt: Keep $100 cash in it at all times. If you get mugged, or lose your pack/wallet/etc, you've got some cash to get you through. These things range from about $10 and up. I bought mine on Ebay, its an unassuming black web belt that doesn't look like anything but a belt.
Whistle: Though I don't carry one, a lot of the girls I met along the way do. Use your imagination.
DO NOT CARRY PEPPER SPRAY, A KNIFE, MACHETE, GUN (unless permitted by local law, and chances are it isn't. **but if you backpack Alaska, it may not be a bad idea!** ) or any other weapon. Not worth the hassle, or the liability.
This is the biggest bone of contention. Unless you are heading deep into the back country, where laundry services are generally unavailable, its not necessary to bring a change of clothes for every day. Do laundry along the way! Save weight! Support your local laundromat!
For 8 days in Costa Rica, i packed the following:
4 pairs boxers
3 pairs light socks
2 pairs heavy hiking socks
2 polo-style shirts
1 fleece vest
1 button-down long sleeve shirt
1 pair cargo pants
1 pair cargo shorts
1 pair, board shorts (swim trunks)
1 pair Teva's (all-terrain sandals)
1 pair cross-country style tennis shoes (never wore 'em.)
1 pair medium-heavy duty Merrel Chameleon hiking boots (wore 'em everywhere)
Now, this includes the clothing I wore down on the plane, IE, the long pants, long sleeve shirt, vest, and requisite underwear. Hindsight being 20/20, a long-sleeve T-shirt or a sweatshirt would have been nice, but not necessary. It did get cold in the mountains, but I didn't mind so much. I would have much rather had more heavy hiking socks than athletic socks, however. Again, live and learn.
Those neat zip-off convertible pants are well worth it, as you have long pants and shorts if the climate calls for it. Again, your mileage may vary.
This was a list for a Central American trip. A Western European or North American trip would be completely different. Take into account the different climates you may encounter. Pack accordingly. If you think you'll be clubbing then bring an outfit that can pass for a club entrance, but still get some mileage on the road, etc.
Which Pack Should I Get?
"does anyone have _____ pack?"
"is pack _____ the right one for me?"
These sorts of questions are all over the boards. Let me clue you in on something: Just like your choice in clothing, cars, women or men, its entirely subjective to your personal preference.
Many folks here swear by their packs. I know that some senior mods/recogs and general users will never own anything but a Dana Designs/Eagle Creek/Kelty/jansport/etc pack.
Here's the advice from the Joker:
Figure out how long your trip will be. Then, go to a good sporting goods store that sells a variety of packs and has a knowledgeable staff, and ask for suggestions based on your size. For instance, a small girl would likely be not inclined to get a full size Eagle Creek Ultimate Journey Enormo-Gigantic Friggin Keep My Life in it for Years Pack. But then again, a simple North Face Bookbag ain't gonna cut it either. Check out REI, Moosejaw, etc. The folks there are good and if its a really good store, they'll have the bags stuffed so you can see exactly how big they are fully loaded.
Personally, again, its up to you. What I can suggest:
1. Internal Suspension with integrated cover for the straps (for checking it into luggage at the airline.) I wouldn't want my pack's straps to get caught on something and dismantled before my flight begins.
2. Front Loading: Allows for easy access to your gear. Top loads are a pain, since you have to empty everything to get to the bottom. Sometimes this just isn't feasible.
3. Detachable daypack: Well, prior to Costa Rica, I was a fan. But since, I'm not. The detachable just didn't have enough room for my hiking necessities and a bottle of water. I thought it was gonna stretch itself apart, and that wasn't good. So next trip, I carry my trusty North Face bag that's served me on many ski trips as Beer and backup glove caddy. But again, YMMV.
An honorable mention are the lines of packs that have a steel cable wound through them for securing to fixed objects. Mine, an Eagle Creek Transcontinental Journey, has one. My cable lock and padlock were always hanging from it, and it was definitely used on occasion. Consider this as a part of safety/security. Nylon webbing straps can be cut easily.
Also, a bag with a ton of compression straps is good for the obvious. That, and the hammock you bought can be lashed to it. Or your sleeping bag.
"Rolling bag or not?"
Again, if you think that your trip is going to be on paved roads, it may not be a bad idea. But if you are traveling into the back country, a backpack is the way to go. Eagle Creek has some convertible packs called "Switchbacks" but all-in-all, its again a personal preference.
Hopefully the above makes some sense and helps you along the way. If you have any more specific questions, dont hesitate to ask a mod or recog. That's what we're here for!