I have an idea for an online list making app. The list can be sorted on any number of attributes (or “sorts”). Attributes can be added at any time and once “activated” you can drag and drop your list to the order you want for that attribute. Then, if you go to another attribute, it again can be drag and dropped into order, but the order is remembered. So if you go back to the first attribute, the items are resorted based on that attribute.