As ever with a new release of Lightroom there are plenty of video tutorials around, some are here already and some are coming shortly.
Luminous Landscape, one of the sites that has consistently produced a full video series for each release of Lightroom, now has an updated set for Lightroom 4. This is in the usual format, where Michael Reichman and Jeff Schewe give the viewer a more homespun (but very in-depth guide to the new release). Currently available for $59.95 (the price will change when the series is complete). This combo release contains a New User series and an Advanced series.
Laura Shoe has produced 10.5 hours of content for her Lightroom 4: Fundamentals and Beyond tutorials. These are available for $49.95 or ($57.95 for the DVD).
George Jardine the original Adobe Lightroom evangelist produces very high quality videos as can be seen by his previous Lightroom 3 Library, Develop, Camera Raw and Photoshop Integration video sets. He will shortly be releasing some for Lightroom 4. Keep an eye on his site!
Lightroom Journal also have a great list of resources and some of these include video tutorials
I will update further as I hear of new video tutorials