Formatting citations correctly for a range of different styles can be tricky. CrossRef Labs has now set up an online service that can take a DOI and return you a formatted citation in the style of your choice.

To perform the formatting, CrossRef Labs uses the citation style language processor, citeproc-js, which supports a wide range of citation styles, such as BibTex, APA, IEEE, Harvard, Vancouver and Chicago.

More details about the service, and what its aims are, is here.