Ms MSE posted a while ago about about how to get experience speaking in public. My Post doc supervisor has set up a summer seminar where her myriad of underlings can present on what they are thinking about each week. It's done very informally, and completely coincidentally, one of the graduate students started calling it an open mic. In fact, after one person has presented, there is the standard awkward moment that many open mics have where everyone looks at each other trying to figure out who will go next.
I really like the format. I've never been part of a large lab that has group meetings. I wonder if this is what they feel like (if run well). There's some heckling, but a lot of good questions and answers and suggestions of directions to pursue. I think my presentation skills would have benefited greatly if I'd had the opportunity to talk about my work like this.
The amazing thing is, that in my field, it seems to be understood that it is impossible for someone who is not in your specific subfield to understand what your research is. This is the main reason I've been given for not having a broad seminar like this. The seminar attendees in this case have a very broad set of interests, that could easily be the set of interests shared by the students of a group of faculty who generally work in the same area. Yet there is good communication among students and insightful questions asked.
I'm encouraging my summer students to attend. I think I will encourage them to talk as well. I think, if I ever land a TT position, I will try to implement something like this with the students of other professors that I work closely with.