extisp.icio.us text gives you a random textual scattering of a user's tags, sized according to the number of times that they've used each of them, and leaves you to draw your own insights from the overlapping entrails.
For an upcoming documentary by Benedikt Bjarnason, RhNav - Rhizome Navigation was used to create animated visualizations of large genealogy data sets...
This is a proof of concept for an animation of tag-volume over time. The horizontal rule represents the passage of time, and the vertical rule represents the overall volume of tags at any given point.