Hi all, I'm a bit ashamed to ask this, but generally while travelling, I only bring with me cash in euros and in some countries (not many of them), travellers cheques as well.
I tried once or twice (in Japan and in Turkey) ATM machines, but found the system not very transparent because we never know the exchange rate and at least before, there were charges for each transaction. Back in Brussels from east Turkey one year, I found out that the rates applied were not fair at all - but this was long ago, maybe 10 years before, since then I'm always travelling with cash.
Is there anyone else here who has these reservations ? Or are you all nowadays only using plastic while travelling ? (Landing in Morocco during a weekend, I am not sure that there will be a bank open in the airport)
I rely heavily on ATM machines---they are almost everywhere. It is true that you do not know the rate before you 'buy' but I have found the rates to be favorable. And yes, there is a transaction charge now (usually $5 US for me) so I get a large amount of money at the time. I have had my account altered so I am able to take up to $1,000 at the time---although I usually don't take that much, and sometimes the machines won't let you take more than a much lesser amount. Travelers checks are kind of a pain to cash---it often takes forever in a bank.

There is always a bank open if an international flight arrives in the night time. At least this held true for me on a RTW even in the remotest places. Others have told me they have had the same experience.
Canadian banks add a five dollar charge on international ATM transactions as well. Traveller's cheques are not as easy to cash in some places as they used to be, and banks charge a relatively high rate for these exchanges. On the ATM withdrawals you get the rate of exchange at that moment. I have found this to be the better deal.
The problem arises in some areas where the machines will not take your bank card but will give you a cash advance on your visa. In that case, you need a numeral pin number for your visa. I have a line-of-credit visa with a relatively low interest rate that I keep for those instances.

exult may i join the club?
i take my credit card along but only for the worst to happen
never a maschine always cash
mashines dont like me and i cant remember the pin number
if the airport your going to has a bank it should be open, have a look in the internet all international airports should have a site with informations

I also rely on ATM machines and found it helpful to check with my bank at home before I travel to get the list of banks to use. At least with my bank, the fees for ATM vary with which bank I use when I am traveling. The ATM fee was less when I used the banks on their list.
That being said, I also take cash, usually tucked away and used only when necessary or near the end of my trip. I still remember watching a guy in Luxor using a ATM on a Sunday and having his card "eaten" Hence, I try not to use my ATM card when the banks are closed:) In general, I have found that you get stuck paying fees not matter what way you choose to exchange money, that the exchange rate using the ATM's is generally pretty good, and that traveler's checks are a pain.
I switched accounts to one that, with a minimum balance, allows withdrawals with no fee. (TD Canada Trust). As I noticed days before my departure, my original card was de-laminating, had two cards made up right at the bank branch within less than half an hour, so I carried two cards if the card would be chewed up.
I had little difficulty in China, Sri Lanka, and Thailand using ATMs, but major problems finding a bank in India that would. This was particularly the case in the small towns where there would only be one bank, and if it happened to be one that didn't accept your card, tough luck! (I ended up using Travellers checks at the money changer in Mammalapurim.) I remember spending one day in Cochin where we must have tried at least 6 banks in a major commercial area before finally finding one that worked.

My personal preference is a little cash for starters and for emergencies and a credit card with cashout facility for the rest. I find carrying largeish sums of money stressful and awkward. Where do you stow larger sums of money sufficient for perhaps two weeks - my bras full already and a pouch is great but add extra money it becomes quite obvious on a person of my build. I usually carry enough for about 4 days and top up on day 3. Also have a couple of old travellers cheques that have been around the world so many times they could find their own way, but they are handy for an emergency if the going gets tough. The last time one was used was during a power outage and no machines available, but the hotel accepted my TC.
I rely almost completely on my credit card - both for paying for goods and services and for drawing cash, the latter only if I find I cannot use my card as often as I would like. I do take a relatively small amount with me in hard cash to see me through the initial stages or in case my card is not accepted at an ATM for any reason. I take two cards along, one a Mastercard, the other (just in case) a Visa card, on different accounts. Theoretically my wife would keep one and I would keep the other in case one of us is the victim of a pickpocket and we have to have the card stopped. If we were not travelling together, I would keep the cards in distinctly different places. I have always found the exchange rate charged to be fair and to reflect the rate prevailing at the time.

I suspect there is a big difference between a trip of several weeks and several months.
We generally head for 2-6 months and prefer not to carry that much cash. However, I always have a good supply of cash and try never to land somewhere without a two-day supply in my pocket (order it from the exchange here at home). On the road I use my VISA card if possible because I collect points and I find their rate works out cheapest. Before I leave, I always pre-load the VISA with enough to last the length of the trip so there are no interest charges. There is a 2.5% charge for using VISA/Mcard out of one's own country but that is mitigated by the better exchange rate and lack of other fees.
In modest places in developing countries credit cards are usually not accepted for payment on rooms or food so for that reason I withdraw the maximum allowable on my ATM card and carry quite a bit of cash all the time. The ATM card usually works out the cheapest - take out your max and like Lor, increase your allowable as you are dinged "per transaction" so you don't want to be withdrawing $100 /day. Fortunately, these places are usually also a lot cheaper so your money lasts a lot longer. If you are heading out into rural areas where there are unlikely to be ATM machines (and don't rely on a report of a single ATM machine somewhere because they break down, get emptied out on paydays very quickly, etc) I make sure I take out a LOT of money. There is no doubt that "money management" is an important part of travelling. It's not like home where you can walk around with 50 cents in your pocket and count on ATMS on every corner and even the parking meter takes a credit card (and increasingly, ONLY takes credit cards :)
When I take money out of a machine I pay attention to where/when/who is around me. Some places, like Nairobi, for example I had a trusted driver from the hotel take me to the ATM and wait while I withdrew. Then I got in and drove away again. I've never been robbed - "scammed" for sure but never outright robbed. It's important to keep your wad out of sight - just what you need for the day on hand.
As mentioned, there are places where your ATM card will not work. Then I pull out the pre-loaded VISA for a cash withdrawal and if it fails, the Mastercard. Some areas of the world (I've found Central America to be so) are much more heavily into Mastercard than VISA. I make sure each has a PIN and that I can remember what it is :) I forget between trips!
Travellers cheques - always have a couple hidden away somewhere but I've found these don't always work out too well. At airport exhcanges/big cities they can be subjected to horrendous fees (10-20% and the 20% was quoted at the Frankfurt airport one trip). I also keep $200 US hidden away as my emergency stash. I think this is likely to be more useful than the travellers cheques. I did try to use my travellers cheques once in rural South Africa and was told that it would take 2 days to process - cheque had to be sent to Capetown for verification. Fortunately a fellow traveller came to my aid and loaned me some cash till I got to Capetown myself.
As important as having enough cash is ..it's also important to "run out" as you are leaving the country because there are places where you cannot exchange it again once you leave the country (and certainly not change) ...so as you change countries let it run down ....but don't forget to keep enough aside for the "departure tax" so many countries love to charge. I almost missed a plane in the South Pacific once because I had failed to keep enough cash back for that, they didn't take credit cards, the exchange/bank at the airport was closed, etc. A fellow traveller came to my aid ...it's a lesson I've never forgotten.
With the decline of the US$ I am wondering how many people are starting to keep Euros as their "cashable anywhere" currency. I've heard the Euros are much better received in Asia than US$ ...any comments?
I prefer using plastic to get cash advances over the counter from banks rather than from ATMs. Also I take cash as £50 and 100Euro notes don't take much space. I bought £1000 of travelers cheques six years ago and I've £800 left which have traveled a long way with me. In the past I've taken gold Sovereigns and sold my blood and my camera when things got rough. What I fear is my card being eaten by a machine or a machine giving me the wrong money and I can't think that doing anything about it would be easy. My card was refused by one bank on my recent trip to Madagascar and the insurance company were not interested. Fortunatly I had other cards and cash etc. There doesn't seem to be an easy system.