Taxi fares are unregulated in Phoenix, except at the airport. The 800-square-mi metro area is so large that one-way fares in excess of $50 are not uncommon; it's a good idea to ask what the damages will be before you get in, since it will often be cheaper to rent a car, even if you are renting for only a day. Except within a compact area, such as central Phoenix, travel by taxi is not recommended.
Taxis charge about $3 for the first mile and $1.50 per mile thereafter (not including tips).
Checker/Yellow Cab (602/252-5252). Courier Cab (602/232-2222).