HAHA! We got an owner's locker as soon as we got DVC and started going more than once a year. We fly, and even though we usually have free checked luggage, it is REALLY nice not to have any checked luggage at all, and OL helps us with that. There is an online inventory on your OL dashboard that I try to update at the end of each trip as we pack everything up again.
DH and I each have a set of (Disney) sleepwear; 7 ponchos (may be down to 6...) for our family of 4; a rotating selection of park bags, string bags, backpacks; misting fans (kids!), a few pairs of waterproof sandals, hairbrushes, feminine products, toothbrushes, toothpaste, SUNSCREEN, kids' toiletries (although they are outgrowing that), extra sunglasses, a couple of summer dresses that I wear at WDW; some Mickey ears, water bottles. some pins for trading. We also have a 4-person set of plastic dishes that we thought we would use when we stayed in studios but which we have not used at all. Old popcorn buckets that we use at the beach/pool. OL is a little bit like DVC, if you have it, you will find more things that you just *need* to stick in it, but the ponchos, water proof shoes, pajamas, toothpaste and sunscreen saves us a lot of space. We probably would never have bought misting fans if we didn't know we could leave them behind in the OL, but we also now regularly use the misting fans to stay cool when we visit in the summer. We don't keep any kids' clothes in there because they grow too fast.