Items I used:
1 Spaghetti Strainer
1 roll of duct tape
Free (graciously taken from wife)
$4.99? (I can’t remember)
$0.99? (I can’t remember)
While if I made a permanent structure it would have much more sturdiness to it, this one worked great. Check out the screen shot pictures. I was able to get a 24% increase in signal strength and 40% increase in link quality. Unfortunately I wasn’t able to get Netstumbler to work with the DWL-122 USB adapter correctly. So actual decibel and wattage information is beyond me. I have estimated by pacing that the distance the signal is traveling is 126.4 feet (38.5 meters). The signal is originating off of a DI-624 AirPlus Extreme-G router, travels through a window, across the yard, and another window.
For more information on DIY antenna design, store bought, and what others have done, visit the links below. There is -TONS- of stuff about it. Especially in the 2.4 ghz band with 802.11b/g equipment.