Here's an article about bathroom etiquette. Granted, it's geared strictly to men and some of the advice is so straightforward ("always flush") that it seriously makes you lose your faith in the power of public restrooms.
Still, I think it's always good to remind people of the levels of acceptability surrounding the world of toilets.
My biggest pet peeve? Using cell phones in the bathroom. In college, one of the girls on my floor would always talk to her boyfriend on the phone while, um, performing certain bodily functions in the public lavatory. That's gross. I don't care how open your relationship is.
Naturally, I also hate it when people don't wash their hands. Even if you are morally opposed to hand-washing, you should at least make an exception when someone's WATCHING YOU.
Once, I was in a public restroom when a lady asked if she could touch my touch my hair. I couldn't tell if she had washed her hands yet, but I wasn't clever enough to think of a quick way to say no. So I relented. That was a really disgusting experience.
Since I'm sure this was probably the most appetizing post ever, I'll direct you to this site, where you can buy a whole slew of edible insects. Mmm.