One thing that helped me was to understand the motivations of those involved. It's easy to think somebody is rude, or showing off, but fortunately I started from a place of deep respect for the capabilities of everyone in my group, and eventually a great affection for them. I saw that we had a few individuals who, if they weren't interrupting, it meant they weren't interested. After I realized this, I started to prize the guy practically jumping out of his chair to take over what I was saying, because it meant he was engaged and excited by it.
Nevertheless, I did often think about the effect on people who might be less self-confident than me, or quieter (we had a lot of students passing through in those days). In the end, if I needed to be heard, I could raise my own voice just as effectively as anybody else in the group -- but not everybody can do that.
It came to a head one group meeting, when a foreign researcher came to present some results. His presentation effectively ended after a few slides, because it got derailed by the back-and-forth of the "audience". I was really steaming and embarrassed.
He agreed to come back the following week, so I sent round an e-mail saying we had all better be on good behavior. I told the group I would bring three notebooks -- one green, one yellow, and one red. The meeting would start with the green one on top of the stack, and if I got annoyed, I would move the yellow one to the top. If the red one came to the top, I would -- well, I don't remember what I threatened, but it couldn't have been very scary, since I had no power.
In the event, the green notebook stayed on top. Not only was the group on strictly respectful behavior for the presenter, but I think it got better generally for a long time afterwards. I think seeing how that behavior affected an outsider gave everybody a little pause, and made us see ourselves better. But again, I think the details of this anecdote show what a great group of people these were. As a junior team member, I felt able to express and act on my disappointment, and everybody listened and tried to accommodate me.