Everyone seems to be concerned about such things as drilling for oil, logging, air pollution, light pollution... the big, high-profile things. What I find more annoying are small effects on the environment.
For instance, take car alarms. Please, take them far away. They're annoying enough when they're themselves (loud, piercing, and less useful than the nipples on a man's chest, since everybody including the police has learned to ignore them), but now they've infected the natual world. A bird which hangs out near my house has developed a song consisting of its imitation of the latest car alarm: a cycle through several annoying noises.