I've been interested for a long time in combining a wiki with a zooming user interface. The idea is to lay out the pages of the wiki over an infinite 2D plain. The user can move them around and resize them, using size and position to convey relationships between items. As one moves between pages, the characteristic behaviour of a ZUI is to zoom out to reveal both the source and the target, and then zoom back down to the target.
Cecily can be found at http://jermolene.com/cecily