I am generally a pedestrian, and in my experience when I am running on a paved path and cyclists go around me, they sometimes say "on your left" which works pretty well, but bells are great.
edit: doh!
edit: doh!
As a cyclist, I don't feel like it works very well. About 50% of the time the pedestrian startles and dodges when they hear you say it. In about 50% of those cases, the direction they dodge is to the left. And this is on the bike path where pedestrians are presumably accustomed to and expecting bicycle traffic.
I still do it for the sake of courtesy (and the hope that it will eventually become a common and well-understood practice), but I don't rely on it and give pedestrians as wide a berth as possible as well.
[NB This isn't a serious problem, but I do spend a reasonable amount of time on cycle paths trying to co-exist with other path users on civilised terms!]