Above and beyond any advice you receive, trust in the catch-cry of the Hitchhikers Guide to the Galaxy, by Douglas Adams:

Before you go:
Go and see the Travellers Medical and Vaccination Centre. Tell them where you are going, and they'll tell you what shots you need and special gear to take (water purification tablets, malaria staff, etc.). And although you will get bombarded with questions, mention the d word anyway, they ask you stuff more out of curiosity for their own sake than to help you.

Insurance
Make sure you get travel insurance for both health and belongings. Pre-existing conditions usually require an excess, around $100 on top of what you normally pay (depending on length of trip and countries travelling to). Holiday Travellers Insurance will cover you (for an excess of course) but obviously deal with a lot fo people with diabetes, so will not ask you tricky questions and are fairly low key about the pre-existing medical (call 03 9882 2958, or toll free 1300 300 132). You will have to get a form signed by a doctor - so allow time for that!!

MedicAlert Bracelet
Just get one, they are corny and you feel very 'special' while wearing them, but when you are travelling alone, it's just best to have it on you. Your parents naturally worry heaps while you are off overseas, and it's amazing how having this bracelet helps them to relax just a little. The symbol is recognised in North America, and the writing on the back will explain things to anyone who can read English.

Good things to take:
Letter from your doctor (just remember at your next appointment) saying you have diabetes and that you take insulin. I haven't ever heard of someone needing to use it, but it may be good for when you're stuck in some remote boarder with custom officials who have never seen an Australian in their life and think you're a bit dodgy.
Medical kit: Just take one with the essentials. For Europe and North America, you'll be fine, but for other places, treatments for water, diarrhoea and gastro are very important.
Cool Pack: One of those Frio packs, which are really really cool. They need to soak in water for a while, then you stack your insulin in and they keep cool for up to 45 hours, before you need to resoak them in water. Nice.
Pen with a light on the end: My sister gave it to me as a going away gift and it was incredibly useful!!

Supplies:
This depends on a couple of things: For short trips, like say you're going to spend a week in Bali and you plan to sit on the beach and not move for seven days, carry what you normally need and don't bother too much with packing twice as much as you would normally use. It's not worth the hassle of carrying extra stuff.

For example, Barry spent a fortnight in Thailand last year, and just carried with him exactly what he needed. It saved on space, and worrying about whether or not his bags were in the sun, losing them or whatever.
For longer trips, you need to be aware of where you are going, the level of development (third world, second world, war torn, super advanced, etc.) and length of time away. A trip to Thailand is no worries if you are sticking to the main populated and tourist regions. However, trekking through remote regions will mean you should be a little more prepared in case something does go wrong. In these cases, splitting your supplies into separate luggage items, or having relatives send you supplies to a location that you intend to visit are a good idea.

Time Zones
Go with the flow (ie. your normal routine) until you stop travelling and have a long sleep, and then start from scratch when you wake again. This is best played by how you are feeling - there are no real formulas to handling this well, and in the end it is no big dramas having your shots a little out of sync for a couple of days.

Food on Planes
Diabetic meals = boring as. Try not to put yourself through the pain. However, by asking for a diabetic meal you do receive special treatment as they put it together that you have diabetes and can serve you meals/snacks whenever you want, including before take-off! Usually, flight attendants are very clued into the needs of diabetics whether you ordered a special meal or not.

Customs
It has been said that Australia is the worst place for dealing with customs of them all! Every country has a diabetic or two residing there, so they do know that you are carrying this stuff for a legitimate reason. This is never a big issue for travelling.

Language
I always memorised the sentence 'I have diabetes' applicable to the country I was travelling in. I didn't use them at all, but when I got home I wowed my parents with my ability to pick up languages and say sentences that they didn't understand. You can work out these sentences through those little Language Guides like Lonely Planet. The word 'diabetes' is pretty much understood, as the equivalent word for each language is derived from the English (or Latin) one (not in Asian cultures though - ed).

Extreme Conditions / Remote Regions
It's sometimes easy to forget about important stuff when you are dying from the heat and can't think about anything else than how to cool down, let alone how your insulin may be travelling. It's exactly the same when you're walking along in -30oC temperatures - all you want to do is save yourself first! But when you do remember, carry a Frio Cool Pack if you are in the hot stuff and away from refrigeration, and in the cold keep everything as close to your body as possible - if this is at all possible. I have spent nights sharing my sleeping bag with my gear - as my body heat was the only reliable source of warmth to stop everything from freezing.

Disposal of gear
Just carry a little empty juice container for your sharps, and empty it when you return home, or if you happen to visit a dodgy toilet in the London underground. Be aware in tropical regions of local blood transmitted diseases that you normally don't worry about here in Australia, by maybe changing your equipment more frequently, and wiping down injection sites before and after.

What if something goes wrong?
Don't Panic! Take is easy, slow the breathing down and maybe curse random objects to release the tension. Hospital Emergency Departments can issue scripts for you, and get you other supplies. Any costs incurred can be recovered through your medical insurance when you get home! Anything that does go wrong will always made for a terrific story. This is half of what travelling is all about: having great stuff to tell your kids one day, and to any interested friends when you return.

• When travelling, extra space in your bags in worth gold: if you can get away without carrying extra stuff: do it! Insulin does go off after a while, so don't take so much stuff that it'll go off by the time you get around to using it.
• When travelling, you only ever think about food, when is the next time I eat, what will I eat, what does this local delicacy taste like, will I have enough money to eat? Etc. etc. It's always about the food. This obsession with food may affect your insulin intake: you may end up using more during the trip. Most importantly, don't sacrifice a travelling food experience just because you may be worried about what it does to your levels: do it, because you'll never get a chance to do it again!
• Get yourself an email address so you can write home and tell them you are still doing okay. Internet cafes are absolutely everywhere. It's better than calling as you don't have to worry about time zone changes, expensive calls and the worrying voice on the other end.

How Much Insulin for a Scorpion? Studying in China by Elise Read
Barbados
Beijing, China
Postcard from Canada Cate Watt
Travel by Alison Tiernan
On the Road with Trudi Haylock
A Quick Guide to Living in London with Type 1 Diabetes by Kate Gilbert