Omnivorous Surfer

Ta-Da List is a free site which lets you create lists online which can be shared. This would work for, among other things, Christmas wish lists (it's coming!). Share with family members and they can check off purchases to avoid duplicates...and you don't have to create different lists to give to different people. Would also be useful for tasks to be completed by a number of people, with each one checking off those (s)he has taken care of.