I currently lead and organize a bi-weekly Philosophy of Science discussion group at the physics department here at Harvard. The participants are mostly graduate students (and some interested undergrads) in physics and biophysics. It’s not easy to get people interested (except if we have some special guest around); I think the majority of graduate students and working scientists want to focus purely on getting more regular science done rather than reflecting on what it “means.”
As the group is physics-heavy, topics like interpretations of quantum mechanics, probability, and naturalness are commonly discussed, although we also regularly do more general philosophy of science such as Kuhn, Popper, Lakatos, Feyerabend, realism vs. instrumentalism, philosophy of logic, philosophy of biology (The Evolutionary Contingency Thesis: Do Biological Laws Exist?) as well as more sociological and “out there” topics such as figuring out the best way to rank physicists, the ethics of climate change, neuroscience, the relationship of Eastern mysticism and quantum mechanics.
The fact that most of the participants have good knowledge of science certainly helps a lot to anchor the discussion. Often we find out that there is less uniformity in opinions regarding common issues in philosophy of science such as realism vs. instrumentalism, although all of us are working scientists. (Of course, I don’t know if our group is representative of physicists as a whole.)
To get started on philosophy of science, I particularly recommend this book: Amazon.com: Philosophy of Science: The Central Issues (Second Edition) (9780393919035): J. A. Cover, Martin Curd, Christopher Pincock: Gateway It contains a selection of short essays (no more than 10-15 pages each) which give a good representative of the important topics. You can pick or choose whichever you like; the papers are accessible even to people with little philosophy background. I have used chapters from this book as discussion material in my group.