I have a swatch "collection" ... I find that I use the same yarns for lots of projects, and when i find a "new" favorite, I knit several swatches and calculat the gauge of each. I write the needle size I used, which type of needle if other than my denise set, and the gauge of each one right on the swatch in permenant marker. I kane them all looped on a keyring. Or, I have SOME of them looped on a keyring... and other floating around the house waiting to be attached...
