We are travelling for a year. One of the hardest things we had to figure out was what not to bring. The amount of fun you have while backpacking varies as the inverse of the weight of your pack.
Here are a few useful things we learned:
1) Bring one book each. Most backpacker hostels have book exchanges so you can leave your book and pick up a new one. Expect that you will end up reading some things you would never anticipate.
2) Bring and MP3 player and load it up with audiobooks. Trains, cheap hostels, and dorm rooms tend not to have good reading lights. Audiobooks work great in these places.
3) Take pictures of your home. I put some photos on my iPod and they've gone over very well when staying with people. People love to see your family and your city. They are less interested in the beautiful places you've been. You might want to make a few different slide shows for different audiences.
1) You can bring a stove and fuel bottle on airlines if they are clean and you don't tell the airline. I read the regulations and they are allowed but airlines insist they aren't. Don't tell them. See #4 below. A stove is the least important bit of camping gear. Consider eating cold food if you are camping a few days.
2) Buy an overbag for your backpack. They cost about $15.00 and keep your bag from getting damaged on the plane. They also make you look less like a backpacker so nobody will ask you if you have a stove. If you are doing some day trips you can stick all your stuff in the overbag and lock the zippers together.
3) Take a sleeping bag liner ($100.00). Sleeping bags are hard to clean so we sleep in a liner inside the bag. The liner is also great if the bed is questionable in a hostel. In hot weather it makes a very nice bag by itself.
4) Bring a day pack. We got a little Black Diamond bag that weighs a few hundred grams and folds up ($25.00). We use it every day and it holds all our important stuff.
6) Bring some antihistamines. If you get bitten by bugs and are itching badly an antihistamine will clear it right up.
2) DON'T go overboard on the synthetic clothing. We brought a bunch of quick drying breathable fabrics and generally hate them. Cotton is the most comfortable thing on your skin even if it takes a while to dry.
3) Bring two sets of clothes and extra underwear. Wash one, wear the other.
4) Buy a Tilley hat. They looks stupid, but we love them.
5) Buy good trekking shoes and good sandals. The best trekking shoes are light hikers. Don't go overboard and buy some big leather boots that you'll have to haul around.
1) Set up a photo website before you leave. We use Picasaweb and paid a bit of money for extra storage. That way you can upload your photos while you are travelling and not worry about them. Expect to spent a bit of time on the Internet if you do this. Uploads are often slower than downloads.
2) Don't try anything too fancy online. You'll have limited connectivity and some countries like China will block some pages (like my home page for example). I planned a fancy homepage with a map, but it was too hard to keep it up-to-date. A blog and a photo gallery are the way to go.
3) Buy a GSM phone and get SIM cards in each country. It costs us about $10.00 per country to get a local phone number and we are constantly using it to call local people we meet. Better yet, the rates to call home are often quite reasonable (generally about half the cost of a local call in Calgary).
1) Most of the discount airlines don't allow bookings through online travel agencies because they don't want to pay commissions. If you want the cheapest flights you can often save money by searching for discount airlines for each leg of your trip and buying individual tickets. The main problem with doing this is that if you miss a connection due to delays they aren't responsible. Solve this problem by stopping along the way.
2) Use the postal service and baggage companies. We shipped 50 lbs of caving gear to China rather than carry it with us. We'll ship it back to Canada when we are done. Plan your trip in stages and ship back the gear after each stage. For big packages you'll want a shipping agent like www.globalbaggage.com. They'll ship things from airport to airport and you can pick it up there.
4) Scan your important documents and put them on your photo site in a private album. That way you can always get at them.
5) If you are going to Visa requiring countries, make a bunch of passport and visa photos before you go. There are plenty of web pages that tell you the specs. Lara did ours on our printer. It's very annoying to hunt down a passport photo place when nobody speaks English.
I hope some of these tips are useful.
Enjoy your travels