Excel
*What I have by category (e/s, glosses, etc)
*What I've grouped (depotted and put together)
*What I want (dont have/never had, with descriptions)
*What I'm running low on

Seems like a lot of work but once you get a large collection it HELPS! I used to have maybe 3 items total but over the past 4 months I've acquired a huge collection and it helps keep me organized. I dont always have ALL of my makeup with me so it's easier for me to just consult my notebook and see what to grab before a job, etc...