All product designers and architects will love this one. The new Carve library finally is making its way into trunk and bringing to us much faster boolean operations. Now interactive cut section animation and non-destructive modeling are doable in Blender. The code is very stable, does not crash as much as the current boolean code and is very fast.
The material system is now also supporting a boolean material. To do this the boolean material (pink) has to be added as a second material to the monkey. As you can see this works during render time as well as shaded view.
To learn more about it, I uploaded a test file here: http://www.pasteall.org/blend/11296
There are plenty of builds for OS X and Windows now available at www.GraphicAll.org.