I could write this myself, but I want to know if it already exists.

Basically, it must fulfill these criteria:

• To reorder items, the user must never have to manually renumber them. That would be annoying, and it doesn't scale.
• Can read from a range of data sources (e.g. a database, a directory on the file system, a text file, another list)
• When the original data source changes, the list must automatically change with it (possibly with confirmation, e.g. if a list item would be deleted)
• Ability to persist the list ordering in some fashion
• Graphical display of list items (so that they can include e.g. images)

Optional extras:

• Ability to modify data and write back to the data source (other than the ordering information)