One often unforeseen costs of traveling is drinking water. Many people opt for buying bottled water, but the cost and inconvenience becomes a nuisance . The way I have gotten around this cost is using a Steripen, which can be purchased on Amazon.com. Its a Ultra Violet light pen that kills bacteria, viruses, and protozoa. Ive used on tap water in Central America for a couple of months and currently (9/29/12) in South East Asia with no illness due to drinking water in either location. As a side note, many of my travel mates have also used the pen with no issues. Its battery operated and all you need to do its swirl the UV wand in the water for about a minute depending on the size of your water bottle and its ready to drink.
Its never fun to wake up in the morning, realize your out of water and need to head to the store to buy a bottle, which you often want to drink the majority of before you leave the store. Simply hit the tap with your Nalgine and sterilize as much as you want in seconds. This will save you time and money, not to mention all the bottles you wont have to throw away.