Zotero is a free software that enables you to collect citations as you do your research. You can build a library of books, articles, websites, mulitmedia files, images, etc., from which you can create in-text citations and reference lists in any of the 1,771 citation styles Zotero currently supports. Once you have established your research collection, Zotero allows you to save, organize, stylize and share your library.
Perdue Online Writing Lab gives detailed information on citation formats. It is also one of the few places that will give you information on how to cite in the text. Type in-text MLA, or in-text APA in the search box to find rules and examples of in-text citation styles.