Penwireless.gumph.org has a how to on making a small WiFi antenna – “A small antenna to boost the signal of a laptop wireless card, that can be stuck to the back of the laptop screen. The design is the same as for the larger homemade antenna, but uses thin RG58 cable and is only 2 sectors long. The size was chosen so it could be housed inside the tube of an old pen, to provide rigidity and protection to the antenna.” Thanks Star! Link.