You don't say where you're going and what water you'll be drinking. Coffeeking's comments are daft, unless you're talking about slightly sub standard tap water. You can get all sorts of nasties from contaminated water.
Iodine is kind of OK for short periods if you don't mind the awful taste but a very bad idea in health terms if you drink much of it, and these days there's no need to use it.
I've used Aqua Mira in the past which has no taste, far fewer health implications than Iodine and is very effective. It's a two part liquid treatment though.
Puritabs are hassle and taste free but won't deal with anything really nasty.
These days I use a steripen if I can. No chemicals at all and it's very effective if the water isn't too cloudy.