If I was him, I'd have put ads up. Frankly, with Park Tool's site being free, and the thousands of instructional videos on youtube, he's just going to lose views. Ads on the other hand (google text ads like Tom suggested would be a good way to go) could be matched contextually to the page being viewed, offering relevant tools or parts. But it's his site, so he's free to choose.
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1964 JRJ (Bob Jackson), 1973 Wes Mason, 1974 Raleigh Gran Sport, 1986 Schwinn High Sierra, 2000ish Colian (Colin Laing), 2011 Dick Chafe, 2013 Velo Orange Pass Hunter