Hi S.,
The second item that 'AV' mentioned is what you need for running 110/120 volt stuff we have here, on 220 volt power they use there. BUT things lke hair dryers use A LOT of power and most STEP DOWN CONVERTORS(which is what the second item AV showed you is) can not handle it without over heating. So... this is what you do.
For your computer, Ipod charger ,camera charger, shaver, basically anything small and relatively new. Look at the power supply for that item. It most probably says somewhere on its' info tag something like'INPUT VOLTAGE 90-240V. If it does, that means you can plug it into just about any power source and it will work safely. The only thing you need is an ADAPTOR that changes our style of prongs to that of the country you are visiting. (now look at the 1st link AV sent you). If any of the above mentioned devices say INPUT VOLTAGE 120V, and there is no mention of any other voltage about or around 220V then you need to use the CONVERTOR mentioned earlier. What ever you do, don't plug a device that is only rated 110V directly into a 220v outlet. It will die, well, actually, about 3 or 4 important components inside will melt very quickly...
As far as a hair dryer is concerned, big hotels have them built into the wall, or available as a courtesy or you can go to the local drugstore and buy one for $15 and use it while you are there. Take it home or leave it when you are done.
So, one more time for review,
input voltage 90 to 220 or 240. use an adaptor that changes plug style.
input voltage 110-120 use voltage step down convertor/transformer.
hair dryer - buy one over there.
Have a great trip.
Keith