I know this is a marketing video,  but the Wndows Presentation Foundation seems to hold so much promise for some really interesting applications.

Windows Presentation Foundation Marketing Video (Hi-Quality)

I am just now starting to dive into this technology, but I am so excited about what might be possible.

I should say I am also excited about the other .NET 3.0 technologies, but they have so much more impact on a backend level that I don’t think the average user would really understand what great things they bring to the table.  It seems with the new WPF apps that should be appearing,  it will be hard to miss the leap forward they offer.