I just found out about Waybath’s Buzz Maker tool.

It uses Waypath’s database to map the fluctuation of the occurrences of certain terms in the blogosphere.

Since they kindly provide the HTML code, I assume they don’t mind including a dynamically generated image: Here’s a example:

It seems, from experimenting a bit, that the big spikes are mostly due to spidering cycles, since they are present in all the keywords I tried. Or maybe they coincide with summer vacations?