When I was traveling between Ireland and US, I would suggest (2). Cingular Wireless and T-Mobile. Since I did my traveling, ATT Wireless merged with Cingular. You'll have to check with them for I believe their are daily fees for their use. The other is T-Mobile which I used. You pay about $30 US for the SIM, activation and about 20 minutes worth of airtime. I'll suggest you look at www.cingular.com and www.tmobile.com and compare their pay as their go plans. As for getting one, like vodaphone, each mall has a t-mobile store or a cingular store. I would then go to your final destination and get the card for 2 reasons 1) it's better to get a local number for people to reach you and 2) They will work with you on additional top up cards if needed. Buying online, you may get charges to ship overseas. Good Luck