I started putting mine in a binder with clear sleeves, roughly sorted by theme.

I recently bought one of those hundred packs from Amazon for like $6 and picked about 30 to keep. Still indecisive about which ones to use, and most of those 30 will probably go in the sticker binder. The rest are in a bag that I'll probably drop in one of those little library boxes for someone else to sift through... or hold onto for like a year and then throw away.