The people over at Price of Travel [PoT] have compiled a list of worldwide taxi rates to help people get a better idea of how to budget for transportation expenses. In order to make the rates more easily comparable, PoT has set a standard distance of three kilometers and then gauged metered rates for a variety of cities (listed below).
The site mentions the usual forms of taxi travel (such as airport trips and the very general "getting around town"), but more often than not taxis aren't really the best means of transport.
For example, transportation to and from airports in many major cities is better off done with the local rail or bus systems (try ~$10 to get to Tokyo by train, versus $100+ by taxi). In more rural areas, however, people likely don't have a choice.