Visual tag map

On Seb’s Open Research, here is what he called “Social software programming challenge #2:”

The linklogging system lets people use labels called “tags” to describe the links they capture. The rich collective dataset of tags and the links they’re associated to enables the construction of something resembling a topic map, with tags as topics and links as occurrences.

Now, uses the right-hand column of tag-specific pages to list tags that are related to the current tag. The details of how relatedness is computed are not entirely clear, but it is probably derived from tag co-occurence in individual bookmarks. Browsing the tag landscape by clicking around tag-specific pages is interesting, but how much more fun would it be to be able to navigate a graphical, two-dimensional map of tags, à la musicplasma or audioscrobbler browser?