When you're running a web site, as previously noted you can spend a lot of time watching your log files to see what's going on. One of the things that go on is that people do Google searches and one of the results points at you. I wrote a little script to run through the log and print out the Google queries that found ongoing.
Food for thought here... I have to automate this a bit, run it once per day or so. I should maybe put it in the little list of things over to your left there along with Copyright and Colophon and so on. Anyhow, here it is.