Here were some good examples from homeworks:
From Ann Coulter:
"One web site defending Bush's choice of a a graduate from an undistinguished law school complains that Miers' critics are "playing the Democrat's game," claiming that the "GOP is not the party which idolizes Ivy League acceptability as the criterion of intellectual and mental fitness." (In the sort of error that resuls from trying to sound "Ivy League" rather than being clear, that sentences uses the grammically incorrect "which" instead of "that." Web sites defneding the academically mediocre would be a lot more convincing without all the grammatical errors.)"

This plausibly is a case of ad hominem, if we read it as attacking the grammatical skills, rather than the argument, of the web site to which it refers.

Thanks to Charles Dee.

From Sam Harris:
"....the city of New Orleans was recently destroyed by hurricane Katrina. At least a thousand people died, tens of thousands lost all their earthly possessions, and over a million have been displaced.... But what was God doing while a hurricane laid waste to their city? Surely He heard the prayers of those elderly men and women who fled the rising waters for the safety of their attics, only to be slowly drowned there. These were people of faith.... Only the atheist has the courage to admit the obvious: these poor people spent their lives in the company of an imaginary friend."

If we read this as arguing that the alternative to one kind of theism is atheism, then this is a false dilemma.

Thanks to John Heagerty.

"Given the amount of documentation showing William Shakespeare of Stratford-upon-Avon wrote the plays one can only suppose that the conspiracy theorist are in it for the money they can make out of peddling their wares."

Note that if there were part of an argument that Shakespeare wrote the plays because the view offered as an alternative is motivated by profit, then this could well be a genetic fallacy.

Thanks to Crystal Boomhower.