I just saw a very elaborate way of sending hints to Google, used on a site that seems to be a standard publisher.
The two non-standard vars used in the AdSense script from this site where google_keywords_url and google_kw_type.
Searching for these with Google, WebmasterWorld shows up as the one and only result. However, that thread is locked.
I now wonder if anyone could help to shed some light on these variables?