Take popsicle sticks and paint them the color of every wall in your house. Carry with you on the go to match furniture, curtains, decorations, etc. I've seen the full paint stirrer version of this but love this portable-sized idea!! I would put the "recipe" for the paint on these chips on the backside of them.
DIY: Window Treatment Bracket Template - when you hang your window treatments, you want them to be hung at the same height, distance from the window, etc. Follow this tutorial to make a template so you only need to measure one time. Saves time unnecessary holes in the walls.