Homebrew 2.4 Ghz Omnidirectional Antenna

Here is an good guide to making a Omnidirection meaning you don't have to point it a the wireless access point you are trying to leach off which is handy if your not sure if one is available!

Excerpt:
"An easy step-by-step guide go making a homemade wireless antenna, for a fraction of the cost of commercial antenna. Uses readily available parts, and requires no specialist tools or knowledge."

Link:
http://wireless.gumph.org/articles/homemadeomni.html

Directional wireless designs:
http://www.turnpoint.net/wireless/cantennahowto.html
http://www.engadget.com/2005/11/15/how-to-build-a-wifi-biquad-dish-antenna/