1. A computer-readable storage device having computer-executable instructions for implementing a method of presenting collections of items, the method comprising: storing a set of items in a hierarchical file system structure, wherein each item in the set of items comprises one or more metadata properties; creating a library to contain a representation of each item having the same type in the set of items; receiving a selection to stack the representations of items based on a specified metadata property; upon receiving the selection to stack the representations: associating at least one representation of an item in the library having a particular value for the specified metadata property with one or more other representations of the items in the library having the particular value for the specified metadata property, wherein the specified metadata property is a property other than the type of item; displaying stacks based on a value of the specified metadata property and not based on the hierarchical file system structure, wherein the stacks represent a group of associated representations of items sharing a same value for the specified metadata property; and displaying one or more options for at least one of the group consisting of: sharing one or more of the items sharing the same value for the specified metadata property and creating a slide show of one or more of the items sharing the same value for the specified metadata property.