The WordPress developers are looking for people to help them with usability testing. At present, they are looking for moderators to run tests, and are ideally looking for people experienced in the area – e.g. those who do it professionally.
If you fit the bill, and have some time to give to help improve WordPress, check out this post for more information.
If you don’t have the experience they’re looking for, it’s still worth keeping an eye on the developer blog for calls for testers in the future.