There are a whole range of smart phones on the market right now, with the Apple iphone arguably the market leader, Blackberry and HTC, Samsung and now Nokia phones amongst others.
Another manufacturer is also coming to light and this is Huawei, the Chinese manufacturer. I do not have a huge amount of information on this company but do know that their pricing seems to be quite competitive - take a look for yourself when you are doing your research.
LG and Samsung also have budget ranged phones so do some of the other phone companies, so in order to get the best priced universal smart phone which is on par with some of the higher brands, check out the description of what you are actually getting for your money. If you choose a network (in the UK like Vodafone), then their pay as you go can also be used in different countries for global roaming, but check the rates of the calls etc first before you get a big bill!