I'm experimenting a little bit with Swivel.com right now - it's a pretty neat site that allows you to create graphs on the fly. You share your data with other users of the site who in turn can use it to come up with their own correlations.

Here's a graph I just made that shows the growing - and by now waning - popularity of the XViD format in the warez release scene:



Note that the actual data for this graph might not be that accurate. Unfortunately I couldn't find anything about DVD-ISOs, which should have been a nice addition to this graph.