Here's the easiest go-green effort I've never done: install a low-flow showerhead.
So the people at Niagara Conservation were kind enough to send me an Earth Massage Showerhead to try out. It's something I should have done a long time ago. It's a 30-second fix and can save a ton of water.
Having not tried it before, I didn't know if it would make showering totally infuriating -- we've all had the apartment or dorm room with a terrible shower -- so I also didn't know if it would irritate my roommates, whom I sort of didn't consult on this matter. Then it became kind of a game and/or prank: let's see if the roomies notice this.
Yep, that's where I live: Right at the intersection of "waste not, want not" and whoopee cushions. If I could have set up a showerhead that would have made a hilarious noise AND saved energy, I might installed that, too.
Having used it for about a week, there have been no complaints from the roommates (though I did admit to changing it, and I even left the old showerhead out in case they wanted to switch back). You do notice a slight difference in the shower, but you get just as clean in the same amount of time.
And it couldn't have been easier to do.
Final grade: 9 out of 10 fresh-as-a-daisy roommates.