> Clicking on one of Ben Shneiderman's treemapping projects reminded me that
> I've always thought treemaps  would serve well as a browsing interface
> for library and archive collections because they work well with hierarchical
I played around with this earlier in the year, wanting to provide a
drill-down into our collections by call number.
For our Education Library's Teaching Collection, I used a three-level
visualisation of items based on Dewey hierarchy, and coloured by the
proportion of "new" (post 2006) items. I never put it online anywhere,
so have attached it here.
Dewey was pretty easy to get labels for the first three levels, and
that seemed reasonable enough for most areas. But the majority of our
items are LCC, and that's where I ran aground. The labels for the
first two letters are readily available, but far too general to make
this interesting. I couldn't seem to find any useful data in machine
readable format. Sourcing another level down from LoC  or Wikipedia
 seems tantalisingly close, but there's a whole lot of manual
effort in turning these (incomplete) ranges into something usable.
oʇɐʞıɐʍ ɟo ʎʇısɹǝʌıun