Learn to Kern with Kern Type
It has been suggested that if you really hate someone, teach them to recognize bad kerning. That way, they'll be forever doomed to recognize examples of typographic ignorance and carelessness that mere mortals cannot see.
But how do you ensnare an unsuspecting victim? One way would be to show them KernType, a kerning game.
The site offers interactive kerning practice where you drag letters within words to distribute the given amount of space. When you're finished you can compare your results with those from a professional typographer, and you are awarded a score based on how close you were to matching the pro's solution. You can also share your solution if you think it is actually better than the pro's.
Each example also has a link to the site where you can purchase the font you're kerning, and the wikipedia article on the font's designer.
In no time at all, your friend/victim will be so well-versed in kerning that they may join the ranks of people who cannot order lunch from a poorly kerned menu.