Something that's been chatted about a lot lately is Copic markers. I love my Copics - even a bad day of colouring turns out okay with these amazing markers. One of the issues I had was remembering which markers I already had in my stash whenever I went shopping for new ones. I am loathe to buy two of the same marker when I could have had two different markers for the same price! As a solution I created this marker inventory sheet which I take with me to the store whenever I've got the urge to buy new markers (I mean...when haven't I got the urge). Each time I buy a marker I colour in the little circle. Its a nice visual to remind me how many I have in a given colour family, or if I've got way more blues then reds.
Actually, I inventory all my supplies on similar sheets (stamps, paper, punches, etc.) to help me keep track of my supplies. I find it helpful to be able to look through my inventory binders when I'm trying to get inspired about a new project. Its easy to forgot what I have and a quick glance through reminds me of some little embellishment or die cut that I bought and haven't had a chance to use yet!