Here's a
link of power by country.
The U.S. (AFAIK) is all 240@60 Hz, but we have center-tapped transformers at the homes so residences can have 120 or 240V. But, because of the length of the wire there's varying resistances so peoples actual voltages vary plus/minus 5%. You see 110V applicances as manufacturers are advertising their stuff will work at the low end; but that doesn't mean your utility is 110 @ 60.
Austrailia, New Zealand, and a couple of other places (AFAIK) are all 230V@50 Hz. The rest of the World (EU, China, UK), as far as I know, is 220V@50 Hz.
It's got an interesting history. The way I understand it is Tesla calculated 240V @ 60 Hz was the most efficient voltage/frequency. Westinghouse went with that and since they were the defacto U.S. monopoly at the time, the US and any place the US has a big influence in is 240V. It was felt that 240V was to dangerous for residences (probably Edison), which is why they have the centertap transformers and two legs of 120V.
In Europe, the German equivalent monoply was using the metric system and built their gear for 220 @ 50. The UK switched to 220 @ 50 after the war to be compatible with Europe.
But I don't understand the history/reason for places like Abu Dhab are 230V @ 50 Hz. Based on what's been said about Austrailian's not noticing, I think that means their old appliances still work. If so perhaps the reason is that being inbetween gives them access to the full range of appliances from across the world (at an efficiency loss, but they can get any look they like).