One very cool new WPF app:
http://msdn2.microsoft.com/en-us/office/bb497969.aspx
It is a viewer for all the Office development tasks that you can do nowadays, and that is not little I can promise!
The second one is an OOXML object model implemented by IndependentSoft. Now I don't want to go commercializing on my blog, but it's great the see the advent of object models to shield you from the low level OOXML details. Now only if it were free....
http://www.independentsoft.com/word/index.html
http://www.independentsoft.com/spreadsheet/index.html
Hope it helps!