Didn't really see anything worthwhile on the first few pages of Youtube results. There's a bunch of useful Adobe-produced stuff at:

http://tv.adobe.com/product/lightroom/

but it's not laid out very well in terms of knowing where to start, or which lessons build on each other, etc. I was hoping for something more comprehensive that started at a high level overview and drilled down. For now, I'll just work through those AdobeTV episodes and hope I can eventually put it all together.