Interesting article and very relevant since I've been conducting bi-weekly usability testing sessions. I've had a lot of success using IamExec.com to find participants for one-hour loosely scripted sessions.

Some feedback: It's hard to tell what's a link as the purple really blends in with the black. The dichotomy between "newbie's" and non-newbie's is a bit of a turn-off and could have been more fluidly discussed.