Usertesting.com (a service I rate very highly) are posting videos to a blog highlighting usability problems with a range of major websites.
Admittedly, it's only one participant's experience of a site, but still interesting nonetheless to observe people interact with some familiar and not-so-familiar interfaces. Worth a look if you're interested in usability testing but have never had the time or confidence to have a go yourself.
Usertesting.com blog - videos of "The Worst of the Web"
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