I just got another check from Google for having Adsense ads on my web sites. Sweet - pays for all of my server and internet costs, and then some... I use up a fair amount of bandwidth because sometimes I often have several hundred copies of my free web books downloaded a day. I also get a surprising number of contributions from people via PayPal for my free web books. I am not sure, but if I stopped consulting and wrote full time, I could probably meet my living expenses by writing free web books(*) and accepting donations. (But, I enjoy consulting too much: I love solving problems). Anyway, I appreciate Google Adsense ads - give them a try yourself.
(*) speaking of which, I have been working such long hours consulting the last 7 or 8 months, that I have not had too much time to write. I am now taking a 4 or 5 month break and only consulting about half time (for a pleasant change), so I will hopefully get some more open content material written. (But I am also trying to wrap up work on a commercial product.) Paul Graham gave me permission earlier this year to use his algorithm in his plan for SPAM paper for extra chapters in my Java AI and Common Lisp Programming web books - that is interesting stuff, and will not take too long to write up.