"You might be interested in the popularity of keywords in Google for a variety of reasons -- you might be doing research on a technology, or you might be trying to optimize your page and get a sense of how many other people are using the
word you want to use. G-Metrics is a service allowing you to track the number of results for a keyword over time.



To use it you'll need to register (just name and e-mail). When you register you'll be sent a "key" by e-mail; this is what you use to log in. When you log in you're presented with the list of keywords from the front page, which you can add to your own watch list.



Interesting, potentially very useful, worth a look.