IBM's new Many Eyes rocks. I experimented with the nptech data last weekend and built this in about 10 minutes. It's a very rough bubble map of the users of the nptech tag. Interesting how it shows the distribution of the tagging activity. Related: Swivel and Data360.
Number of times "nptech" was tagged, by del.icio.us username
My Many Eyes account is here. (You can get an RSS feed of my visualizations.)
EDIT: Just to be clear, the usernames in the plot above do not reflect the actual number of contributions (the top posters are not getting credit for more than 100 posts each), because of a bug in del.icio.us, which I have discussed previously.