I can't explain why, but I have neglected to post an item about Zotero before, and that was a massive oversight on my part. If you've ever found a book that might be useful for a research paper or project of any kind and wished you could have kept all the publication information but didn't remember the correct citation form, this is the program for you. And did I mention that it's free?
Zotero was created by historians to be used by historians, but it's also wonderful for anyone writing a paper in any discipline. It can be used to cite in MLA, AP, or Chicago Manual of Style (the style used by historians) or any number of other citation styles out there. So, if you were using one source for a history paper on slavery--say, a slave narrative--and wanted to use it for your English paper on writing styles, Zotero could insert a footnote and bibliography entry in MLA style for the English paper and Chicago Manual of Style (CMOS) for your history paper--all with only one keystroke of change.
Zotero is a bibliography software. Every time you find a book or article or other type of source, an icon appears at the top of your Mozilla Firefox. Click that icon and Zotero does all the heavy lifting for you: it instantaneously downloads all the necessary information about the source and keeps it for you--forever. You create an online account and, presto, wherever you are that has Firefox and a connection to the Internet has your bibliography. Here is a screenshot of the bibliography I'm building for my latest research project on movie violence: