Not only am I inundated with ads in Gmail, but they seem to be reading my mind.
Is there any way to turn this off or otherwise change this "tracking"?
The Firefox extension AdBlock Plus removes them just fine, although the equivalent in Chrome does not.
Regarding what you call "tracking", that is just software finding keywords in your emails and displaying appropriate ads. Obviously no personal information is given to advertisers and no-one is reading your emails.
If you purchase the premium edition of Google Apps, ads will be disabled. Disabling ads via other means may be a violation of Google's TOS (and they'll still be doing all the mind-reading, just invisibly)
An application called Rapportive effectively replaces the ads on the right side with something more useful. (User notes on the contact's email) Not certain of the legalities of this. Also not sure if it is THIS app which is effectively hiding the ads or some setting or feature I have enabled, but this is worth looking at anyway.
For the right side ones, you can always just enable the chat to appear on the right. Then your only ad will be the one above the archive/report spam/delete/etc buttons.
Well, one work around I've seen is the "magic words" from Boing Boing. Basically adding catastrophic words such as "murder" "suicide" in the email body and Google won't show "related ads." Of course this work around isn't the most practical.
If you are using Firefox, you can use Adblock Plus addon to eliminate those ads.