This is what I know:
1) Don't wear bright colors, stick to conservative colors or dark colors (brown, black, gray, coffee colors).
2) Girls: minimal makeup, avoid wearing perfume, simple hair style
3) Guys: well shaved, tie, avoid wearing cologne
Girls can wear long pants or skirts but the skirt should be close to knee-length. Avoid wearing short sleeves.
Guys should be wearing a professional business suit with a tie.
Basically dress like you are going to a funeral, business conference or church. Your answers and personality should stand out, not your outfit so don't do anything crazy. You don't have to dress in the typical black outfit and white blouse (I hate blouses), you can still be creative and stylish but just tone it down a notch. Your outfit isn't going to sell your interview, it's just going to represent you as a professional, serious, and credible applicant.
For girls you can go to either The Limited or Express (or Lerner New York) to get really nice blazers and pants for an affordable price. They have really chic and stylish but professional outfits for young people. I brought my jacket at The Limited for $150 and the pants for $68. So it's not bad at all. Shoes should be closed toe and closed in the back. Good luck with your attire.