Here is a list of free online citation generators. These generators allow you to enter your resource's (e.g. journal article, web page, book) information and then it allows you to create a citation and bibliography (works cited) reference that you can copy and paste into your paper.
JAMA and Vancouver styles, often used for medical articles, are available in BibME, Citation Machine, and EasyBib. Select the "Other" category and search by style name.