Hey HSBNE,
With lots of people starting to get interested in building 18650 battery packs I thought I’d put together a useful resource on the wiki. I’ve documented (based on my experience) the best suppliers, places to take your old cells and general disposal tips.
I’ll add to it over time but you can find the page here: https://wiki.hsbne.org/resources/18650s feel free to add to it or leave any feedback.