I'm a great believer in skimmer socks - use them all season long. They're invaluable in the spring - you wouldn't believe how much pollen ends up in your pool until you remove the sock and find a snowball-sized, brownish clump of what resembles fine cellulose - on a daily basis for a full month or so, mind you. They also excel at catching cottonwood seeds. I live in the Saint Louis area, where cottonwoods are common. Our subdivision is ringed by a ravine thick with them.
I mainly use the regular, white cloth socks, but I also use BioGuard Skim-Mor socks. These are blue in color when new - the color is due to a coating of mycelx, a compound that was developed for use in cleaning up oil spills, as well as water filtration. They attract all kinds of volatiles and oils - including lotions and sunblock. I use them when I expect heavy bather loads, but also use them generally though July and August when the sun is intense and sunblock usage is intense. Mind you, you'll still experience some scum build-up along the waterline, because some of the lotions and sunblock will adhere to the pool walls before being drawn into the skimmer. They're more expensive than regular skimmer socks, but I truly believe they prevent most of that stuff from making its way to the filter (sand in my case). Oily residue and calcium build-up are two of the most common causes of impaired sand filtration.
Now that I think of it, I probably spend more on skimmer socks than any other chemical or maintenance item during the season. The only other things I use are salt (SWG), calcium chloride, CYA, bleach, baking soda, dry acid and vinyl cleaner (for the scum along the waterline) - and, at closing, polyquat and marine antifreeze. I generally don't add much, if any, calcium chloride, CYA or baking soda after opening, but I do go through a few 7-lb jugs of dry acid/pH minus each season. I am thinking of trying muriatic acid to keep my pH in check next season (pools w/ SWGs, or salt water chlorine generators, exhibit pH rise due to the aeration caused by hydrogen outgassing) but dry acid is convenient and - in my opinion - less worrisome from a safety perspective.
I really need to keep track of my chemical and maintenance expenses next season. I'd probably be surprised at how much (relatively) I spend on those items, as well as replacement reagents for my Taylor K-2006. But since I avoid pool store chems, do my own testing, maintenance & cleaning and open/close myself, I figure my seasonal costs are much less than those of the typical pool owner. The only time I shop at a pool store is when buying Skim-Mor socks, and I have to concentrate to avoid rolling my eyes when listening to some of the advice they dole out to unwitting pool owners. That's not meant to sound condescending - it's a testament to what I've learned at TFP and The Pool and Spa Forum.