An open source, collaborative Dewey replacement?  That sounds pretty cool...

The Dewey Decimal System® was great for its time, but it's outlived that. Libraries today should not be constrained by the mental models of the 1870s, doomed to tinker with an increasingly irrelevant system. Nor should they be forced into a proprietary system—copyrighted, trademarked and licensed by a single entity—expensive to adopt and encumbered by restrictions on publishing detailed schedules or coordinating necessary changes.

Thingology (LibraryThing's ideas blog): Build the Open Shelves Classification

The related discussion forum has lots of good conversation about all things classification.