Part of the problem with holiday gift-shopping is the worry that the gift is something that your friend or family member might not want, need, or find special. Giftster (Android, iOS) gets around that by serving as a gift ideas registry that you can sign up to with friends and family, allowing each user to create a list of items they'd like or prefer, and which friends and contacts can mark as something they've already bought. Users can record things like clothing sizes, rank gift ideas, and set the visibility of particular gift lists, and set up a Secret Santa among particular groups of contacts. The app's also great for other occasions like birthdays, weddings, and other gift-giving celebrations where you don't want to double up.
MORE: Check Out Great Gift Ideas from Tom's Guide