I read Petzold's blog from time to time and I realized recently he has posted a lot of good 3d content.

http://www.charlespetzold.com/blog/2006/12/140114.html
http://www.charlespetzold.com/blog/2006/12/160115.html
http://www.charlespetzold.com/blog/2006/12/171020.html
http://www.charlespetzold.com/blog/2006/12/220812.html
http://www.charlespetzold.com/blog/2007/01/190146.html

and finally it's coming WPF 3d book by Petzold.
http://www.charlespetzold.com/blog/2006/12/270206.html 

5-6 years ago, there's a trend to have app written in irregular window, layered window, pixel opacity or different chrome. Then came a wave of products doing just that. I think what's coming next (in my own opinion) is the application have multiple layers and 1..n layer that display 3d visuals. For example, a TV app with tv controls in another layer in a Viewport3d floating in 3d or even animating a bit :-)

can't wait for his 3d book ...