The Stony Brook Physics department is quite good for a variety of subjects and is unique in a way. The program has about 40 graduate students/year, probably 70% international, so it is quite a large and diverse program. Way back when, in the early 70's I believe, a young mathematician (James Simons) and the renowned C.N. Yang began dialogues between the math and physics department. These dialogues related to modern gauge theories and were mutually beneficial for both parties; much of what physicists were trying to develop had already been done. Conversely, mathematicians were thrilled to learn that the notion of fibre bundles had such a natural place in the physical world. What started as informal discussions led to the development of the (now called) C.N Yang Institute for Theoretical Physics (YITP), which is one of the world's premier research centers in string theory and mathematical physics. So Stony Brook is a fantastic option for students interested in these areas. It is also ranked as one of the best physics phd programs (usually in the top 20) with particularly active research in Nuclear Physics, Mathematical Physics, Statistical Mechanics and Lasers/Optics among others.
Admissions: Like most departments, much of this is a mystery, but here is some hard data (taken from the department's website):
Average GPA: ~3.5 (Minimum GPA 3.0)
Average GRE: Verbal: Mean = Median = 560
Quantitative: Mean~760; Median~ 785
Physics Subject Test: 800 (72nd Percentile)
Obviously, these represent but a small part of what it takes to get in. Recommendations here are by far the most important aspect of almost any graduate applications, but the numbers about give a rough estimate of necessary (not sufficient) conditions to be admitted.
Students admitted to the PhD program are all offered funding by the department for the first year, usually via a Teacher's Assistanship, which typically involved grading labs. After this, funding is typically through the advisor the student picks. For fall 2007, the average 9-month salary for incoming student was $15,700, which is a bit meager, but will suffice with summer support which is usually also available
One important thing to keep in mind through is it is not wise to come here (or any school) intending to work with one particular advisor. There is no guarantee that you will be able to, and sometimes, it's impossible to for reasons completely beyond the students' control (e.g. the professor has too many students already). So it's important to be flexible.
I would be happy to answer any questions that people have.