There's a right turn right by my house that i often signal to let drivers know I'll be turning. It's a narrow road and cars are anxious to pass. They chill out when they know i'm turning soon.

If I were to change lanes from the left lane to the right lane, i also would signal with my right arm. This happens to me more on a pedicab than on a bike; when i'm pedicabbing I use the bikes electronic signals and also arm signals when I want drivers to be sure of my intentions.