Those of you who are either wearing White or Black Hats already know the skinny, so y'all are free to post links in the comment section, if you wish, to further the education of the people who are not yet in the know.
I'm posting this not to encourage people to maliciously hack wireless networks, but because knowledge is power. Many people are at the mercy of hackers, and not all hackers are the local bored teenager just out for a lark.
Many work for corporations and governments.
I think many of us understand exactly where that puts us.
This site makes available, free for download, a DVD that you can use to boot your laptop or PC. It comes optimized for hacking wireless networks. All the tools you need are there. This program will not alter your hard drive, delete, or overwrite your files. It installs nothing on your PC unless you specifically install it. It runs off the DVD.
Be sure to read the "How To" section, the Frequently Asked Questions, and if you want to become a total expert on the use of the tool, check out the Training they offer.
Finally, download the ISO image of the DVD
If you do not have a program that will allow you to write an ISO image to disk (this isn't copying and pasting to a blank disk) such as Nero or other similar programs, you can get a free ISO burning utility at ImageBurn (click this link to go to download page).
Hack your own wireless network to get yourself up to speed and familiar with how the software works. I think you will see how thin most people's security really is, and many government and corporate systems are not much better.
If you're looking for a brute force password cracker, check out CUPP over at Remote-Exploit.