I recently had my windows changed. The workers spilled what I only know as "Builder's Foam" on my wall (and floor, but I fixed that). I have worked with this material myself and I know from experience that cleaning it off is an effing mess - unless you manage to clean it before it starts setting/puffing up.
Question: What is the best way to clean Builder's Foam off semi-sensitive surfaces? (example: Painted walls, wallpaper, hardwood floors)
The workers in question seems to have solved it with mechanical/abrasion of the wall and then repainting. I cleaned the floor with careful application of a razorblade and light brushing.
 If Builders Foam is not understandable to everyone: It is a liquid-ish insulation/setting material that is often used to either insulate places you can't really reach or as a fast way to insulate around a window while at the same time providing structural support. It is blue, and it slowly "puffs up" after you apply it, setting in a foam-like rigid space-filling... foam. I don't know it's proper name, bonus points for identifying it...