The typical range of 802.11 wireless systems varies because Wi-Fi signals are very susceptible to physical interference from walls, floors, ceilings and even people. In fact, it is not unusual to get a stronger signal when farther away from a wireless access point, since these signals tend to take very circuitous and strange routes because of physical barriers. All in all, though, you should expect to get a signal and wireless connection within 300 feet of a single wireless access point. This is why most companies install multiple access points to extend wireless access and eliminate "dead zones" around metal staircases and elevators.
Interestingly, a number of companies are working to expand Wi-Fi access by creating metropolitan networks that offer connections within a 30-mile bubble by creating a mesh network of access points.
Go on to part 5: The cost of a wireless network