Mike on Ads is a blog by an ad-technology insider on ad servers, real-time bidding, revenue, and online advertising scams.
HN commenters call it good, though sporadically updated, and link it for explanations of the Punch the Monkey scam and how ad targeting uses cookies.
This issue is nine years old at this point and has been published, republished, and blogged countless times. I yearn for the day it stops wasting space on the front page of news aggregators.
A partial bibliography:
2000:
http://bugzilla.mozilla.org/show_bug.cgi?id=57351
2002:
http://seclists.org/bugtraq/2002/Feb/0271.html
http://bugzilla.mozilla.org/show_bug.cgi?id=147777
2006:
http://portal.acm.org/citation.cfm?id=1135777.1135884
http://portal.acm.org/citation.cfm?id=1135777.1135854
http://jeremiahgrossman.blogspot.com/2006/08/i-know-where-youve-been.html
2008:
http://azarask.in/blog/post/socialhistoryjs/
http://www.mikeonads.com/2008/07/13/using-your-browser-url-history-estimate-gender/
CPMs vary widely -- from $0.001 (yes that's 1/10 of a cent) to $40-60 for highly targeted verticals.
Educators don't have so much money to spend. It depends on how motivated and targeted your audience is, and how good of a sales team you have to leverage that audience (if you were thinking AdSense, think again. Unless your audience is mesothelioma educators). The only way to get a $10 CPM these days is with direct/premium sales.
Some reading:
http://www.mikeonads.com/
http://andrewchen.typepad.com/
http://clickz.com/experts/
http://ecpm.typepad.com/
I heard about this last year, when I read this article:
http://www.mikeonads.com/2008/07/13/using-your-browser-url-history-estimate-gender/
Basically, it uses the socialhistory.js and some statistics to estimate whether you are male or female (which is useful information to advertisers).
EDIT: Here's the HN story on that site: http://news.ycombinator.com/item?id=248558
if you click on the x in the top right corner of the ad, theres an about this ad link that will give you details on who generated that advertisement.
http://www.mikeonads.com/2010/02/22/rtb-part-iii-cookies-user-data/ this describes roughly how they identify you.
Old but related: Using your browser URL history to estimate gender
http://www.mikeonads.com/2008/07/13/using-your-browser-url-history-estimate-gender/
Seems like i'm 50% male 50% female :D
All friends and acquaintances:
http://reactionwheel.blogspot.com/
http://www.cogmap.com/blog/
http://mikeonads.com (sporadically updated but good)
http://ecpmblog.wordpress.com/