Laughing reading some of these. Here I thought Sophie was semi-lunatic, yet see so many that she barks at too! I guess she's pretty normal! Here's what she barks at:
Anything having to do with cleaning the floor - broom, vacuum, steam cleaner AND dustpan!
Ringing phones - cell phone and home phone, but she immediately stops when the phone is actually answered
TV - random stuff, but almost always other dogs, football and the GEICO gecko (Yes, really. Every. Time.

)
Random happenings outside - predictably, garbage pickup, UPS/FedEx, deer, squirrels and birds, as well as other unseen things (I call them her imaginary friends)
Doorbell - thankfully, she seems to have outgrown TV doorbells

Thunder and fireworks - tried the Thundershirt, if anything it made her more annoyed

The grinder/chopper and the mixer
And the ABSOLUTE WORST is taking out the garbage! To say she barks is putting it mildly. She gets upset, barks, runs around the kitchen, tries to bite the garbage bag, etc. She's done it since she was a puppy, and I can't figure out why she does it or how to break her of it
Small victories: she's outgrown barking at the wind, heavy rain and the reflection of the TV in the window at night.