A new can of wall paint comes with a paint stirrer or two. I use them and I save them. Because I paint my walls often, I have lots of stirrers. I was about to thin my collection when I realized that these paint stirrers are a great record of the colors I have on my walls and trim. If I need to match the paint I can take the paint stirrer to the paint store and get an exact match - which is a lot easier than trying to take in a piece of the wall :-).
I drew a light, level pencil line on the wall in my utility room. I drilled a hole in the end of the stirrers with current paint colors. I wrote pertinent info on each stirrer and hung them with small nails. It's nice to see them all lined up as time I come and go.
Wouldn't you know it - Martha does this too! I just looked through a "how to paint" slideshow at marthastewart.com. I hate to say it, but her stirrers look better than mine - and she's recorded more info on hers. Her paint can is tidier too. But she has a staff of helpers and I don't!