I was trying to get bubbles flowing through a maze-like path, and not having much luck with Emitters. Then I ran across a thread at Creative Cow that recommended using a Replicator. In just a few minutes, I had this first test happening! It is very close to what I am after.
Next, I want to add some jitter to the bubbles. I am going to try animating the control points of the bezier curve. Anyone have any other ideas on this?