It's been said many times in different forms, you're not trying to find a mate or get Bill Cunningham to take your picture. You just want to dress so that no one actually notices how you're dressed, and focuses on your competency.
In terms of men's suits, Brooks Brothers has been mentioned in both a positive and negative light. I would have concur with those who suggested it was very appropriate for interviews. There is actually a world of difference between dressing fashionably and dressing professionally (unless your profession is fashion or entertainment or something). Brooks Brothers are sort of a major standard in conservative men's fashion in the US. That's important for a couple of reasons. One is that being conservative is a good way to have people not think about your clothing, and focus on your main attributes as an applicant. Secondly, it means that the clothes don't go in and out of fashion quickly. Brooks Brothers can be quite expensive, but as noted they do have periodic sales, or you can just use it as a standard example to see what is reasonable. Also, they do have a cheaper "Outlet" brand clothing, and those outlets themselves have sales, which would be even more affordable. Some people will tell you the quality of the outlet branded clothing is not as good, and that may be true. However, for an interview suit, you may only need to wear it a few times. They also sell women's clothing, which is also in s similar vein of being quite conservative. Anyway, their staff have uniformly been very knowledgeable about dressing professionally, both at the main stores and the outlets. If you are not very knowledgeable fashion-wise, you can go in and tell them that, and they can hook you up and dress you in a very conservative manner.
For women in particular, I also think the store Theory (it's in some major cities) has a great line of conservative, but attractive professional clothing:
http://www.theory.com/womens-suits/womens-suits,default,sc.html
http://www.theory.com/womens-classics-theory/womens-classics,default,sc.html
Having accompanied women shopping there for professional clothing, I was really impressed by their sales staff. They had some great advice about how to put together different outfits using conservative clothing staples, and then how to repurpose the same clothing for different situations. Granted, I am getting far out of my depth once I come to be talking about women's clothing.
It might be a bit of a cultural difference, but when I've been in Asia, essentially every professional man and woman seemed to be in a black suit. It also seems to me that it is more acceptable for women to wear black suits for things like interviews in the US. Maybe because things like softer more textured blouses or jewelry make the outfits appear less stark.
That being said, I would agree with some of the previous posts about the importance of being somewhat comfortable in your clothes and interview suit. It doesn't hurt to wear it a few times in advance, so you get comfortable in it, and don't look like someone playing dress up.
I typically wear very soft shoes (or even flip-flips when I am not doing something clinical), but when I dress up, I have much firmer shoes, so I prophylactically use 2x2 bandaids or something similar to prevent blisters. Often on interviews, you have to walk around a lot and they often give you a tour, and you don't want to get a blister.
I have obviously never interviewed anyone for a residency slot, but I have interviewed people for a number of different positions (and for school admissions). For better or worse, part of what the process of judging someone's clothes for an interview is about is seeing if they can get the message and conform in certain situations. Depending on the position, you often want people you are selecting to be able to sometimes just quietly conform. Sometimes you may want exciting new ideas, but sometimes you just want them to do what is expected of them, and part of doing what is expected is being able to understand the greater social cues of what you should dress like for an interview. At the the end, I really agree with muleta4. It's not that you can't wear whatever you want, but the reason this thread exists is that there seems to be a base expectation that you can dress a certain way for interviews. If the person interviewing you doesn't feel like you can do that, they may question your ability to fulfill other expectations they have for you. Or they might not care at all. However, I have never heard anyone ever having trouble interviewing by being too formal; you look earnest. The same is true of showing up overdressed for a new clerkship or anything else. People may tease you about it on your first day, for being too formal, but I don't think anyone holds that against you. On the other hand, showing up very informal can potentially hurt you. In the same way, showing up in something exotic, different, or flashy, can work against you. I would note that there may be some groups that do creative things, like art or design, or some tech companies who expect everyone to be in a hoodie and cargo shirts, and where wearing a conservative suit might count against you, but that is not medicine.
Good luck in your interviews! I hope you can find some clothes that you find comfortable and also minimize your anxiety about the interview process.
