I have a large 3 ring binder with divider tabs. It's Jan-Dec and then theme based units unrelated to seasons or holidays in the back in alphabetical order. I use a LOT of TPT stuff. LOVE that site!
I keep a small tote for each season/theme in my daycare closet. Everything is laminated, and I just reuse now and photocopy (from my binder) any of the 'consumable' stuff.