My Sunday afternoon project this weekend was to add a bit of jQuery pixie dust to the tag trend graph page. The new Stack Overflow Tag Trends page allows you to choose which tags to compare and produces a graph interactively. You can also capture a link to a particular graph, for example the history for the homework tag is amusing.
Available tags are those that have been used for 100 or more questions (1835 tags total at the moment).
Here's a recent newsworthy graph: