This page details the construction of a biquad antenna. The biquad antenna is easy to build, and provides a reliable 11dBi gain, with a fairly wide beamwidth.
A small antenna to boost the signal of a laptop wireless card, that can be stuck to the back of the laptop screen.
alles möglich über wifi-devices and antennen tuning
The W1GHZ Online Microwave Antenna Book
A tin can waveguide antenna, or Cantenna, may be just the ticket. This design can be built for under $5 U.S. and reuses a food, juice, or other tin can.