DIY Range Optimizations
USB-Wi-Fi adapters, food container "Cantennas", parabolic reflectors, and many other types of self-built antennae are increasingly made by do-it-yourselvers. For minimal budgets, as low as a few dollars, signal strength and range can be improved dramatically. There is also a type of optimization by polarizing the signal to achieve a planar coverage like a plate. Many of these high-gain aftermarket modifications are technically illegal under FCC and other regulatory guidelines.
Long Range Wi-Fi
For more details on this topic, see Long Range Wi-Fi.
Recently, long range Wi-Fi kits have begun to enter the market. Companies like RadioLabs and BroadbandXpress offer long range, inexpensive kits that can be setup with limited knowledge. These kits utilize specialized antennas which increase the range of Wi-Fi dramatically, in the case of the world record 137.2 miles (220km). These kits are commonly used to get Broadband internet to a place that cannot access the service itself.