IEMs should stay in the ear, unlike the "normal" earbuds you mentioned. With foam ear pieces, these in-ear monitors can be quite secure and comfortable in the ear. Flanged tips can take some getting used to, and for me the fit changes, which affects the sound, but flanges can provide really excellent isolation.
Excellent value, excellent portability, very good isolation and detail = Etymotics ER6i. My current ultra-portable travel set-up is a second generation Nano with the ER6i's. I don't use my Etys as an everyday earphone, but factoring the cost into the price of airline travel, they are more than worth it. Some kind of noise blocking or cancelling earphone/headphone would be essential for such travel ... remember, the advantage of such 'phones is that you don't have to turn the volume up to 11 to hear well in a noisy environment.
Of course, you can do much better than the ER6i's, but there is a law of diminishing returns.
For good "everyday" canal phones (insert into the ear, but have different drivers and isolate less than IEMs), look into the Creative EP630 (excellent value), and for very good ones look into getting the Mylarones from Jaben in Singapore (free international shipping, I believe, and excellent customer service). Canal phones generally use soft silicone ear pices that are usually less intrusive than flanges, but they don't isolate as much.
In addition to the Etymotics, some good IEMs would be the Westone UM1 (good isolation and supposedly the most comfortable, but unremarkable sound ... depends on your needs) and the Futuresonics Atrios.
At least think about in-ears (I wouldn't travel without them) -- they are simple to carry around (vs. headphones) and they block out noise "passively," so the sound is what's produced by the 'phones ... there's no "competing" headphone-generated sound to counter ambient noise.
Edit: Of course, most of the "steals" are obtained online. You might not have time for that. Over-the-counter options are limited vs. buying online, and prices tend to be higher. A real steal is the JVC Marshmallows, which in the U.S. can be purchased in an electronics store (maybe Curry's, etc., would have them and the Creatives ... check around ... the Sennheisers that are similar to the Creatives are a bit overpriced, but they might do the trick for you as well). But for higher-quality earphones, look into the ones already mentioned, if you can.
Oh -- and in-ears can help meet your needs much more economically than active noise-cancelling headphones, and they should block out noise better than closed headphones that have to clamp tightly on your ears/head to block out some noise.
