Just a quick note to say that Vivek over at [url=http://www.securitytube.net]securitytube.net[/url] has posted 2 wireless security challenges and will soon post a "mega-challenge". They're a lot of fun and a great way to learn more about wireless. If you're new to wireless security, I would watch all of his Wireless Security Mega-Primer series from the beginning. The easiest way to get to the challenges: Click on the Groups tab and then "View all videos" in the WiFi megaprimer series.
SecurityTube now has a certification based on their wireless videos: http://securitytube-training.com/certifications/securitytube-wi-fi-security-expert/ Testimonials look good.
SecurityTube is great. Vivek has done so much for the InfoSec community :)