I have a bell on my commuter. People always seem to smile when I ding it to pass. It's worked well.

On my road bike, however, I don't have a bell. I call out "(however many bikes) on your left."

I wish it weren't frowned upon to have a bell on a road bike. Maybe I should get one that I can just slap on whenever we're doing a slower trail ride. The bell sounds friendly and is easy to hear. In fact, my DH has often commented that he wishes he had one. If he's riding in front of me on the path, and I'm on the commuter, he'll give a wave to me when he's ready to pass and I ring the bell for both of us.

I know I shouldn't care if hard core road riders would never put a bell on their bikes, but (sigh...) I do.