We've talked about these videos a while ago. Microsoft has since added a few more videos, each of them offering a detailed look at not only the new technologies but the potential applications for them. All of the presentations look at Avalon, Indigo, and other technologies to be featured in Longhorn.
Telecoms Video : "In this demo, Carter depicts a Longhorn call center application that coordinates internal and external Web Services to assist a stranded motorist."
Government Video :"Describe[s] how Accela helps cities set the bar for next-generation Emergency Response Services. Government agencies, citizens, and businesses collaborate efficiently to prepare for, respond to, and recover from emergencies by taking advantage of the advanced data, communications, and visualization capabilities in Windows. This video covers technology to be delivered in 2005, as well as demonstrating platform advances coming in Longhorn in 2006."
David Weller is the commentator on most of the videos, and has an interesting blog here.
View: Longhorn Concept Videos (require WMP 9+)