Checkser: a wiki for checklists
Checkser is niche application of the wiki concept: users create/edit checklists for topics ranging from "What to look for when buying a home" to "Things to do before leaving for a vacation." The checklists are useable (you can click checkboxes to mark items), and editable anonymously or with an OpenID signature.
While editing a checklist, you can drag/drop list items in whatever order you choose. You can also provide a "Read More..." link in case you want to offer a preview of a more extensive list found elsewhere.
Like any good wiki, you can view the history of edits for the checklists. Our favorite list so far is the Web 2.0 checklist.
[Thanks Marijn Deurloo]