AARP says these categories are items in high demand by garage sale customers:

www.aarp.org/money/budgeting-saving/info-2015/best-yard-sale-items-photo.html?cmp=BAC-OUTBRAIN-MONEY-SLIDE-DSO_38531300_12+In-Demand+Items+to+Sell+at+Your+Next+_2642406#slide1