You'll find VidZone in the Music section of the XMB. A quick download later and you'll have access to its launch library of "over 10,000" videos.
Artists in that launch lineup include Pussycat Dolls, Britney Spears, Fatboy Slim, Black Eyed Peas, Glasvegas, Dizzee Rascal, Pink, Noisettes, Ne-Yo, Armand van Helden, Tori Amos, Akon, and hopefully some other decent artists Sony neglected to mention in their press release.
VidZone lets you search the library and create playlists, although you'll see interstitial ads popping up between songs as well as on the library interface (see below). That's why the service is free.
PS3 owners, let us know if you're checking out VidZone tonight and if it's any good.