ZoteroBib is a free bibliography maker, that will generate in-text citations or bibliographies into 10,000+ citation styles. It is a simpler option for those that are interested in the features of a citation manager but don't want to download any software or create an account. Citations and bibliographies that you generate will be temporary, and not stored long term or permanently.
Because it is a standalone tool not tied to a particular database or search engine, you can use it with any resources gathered from any source (e.g. library items, websites, Google Scholar, research databases, even print items on your bookshelf!).
If you are looking for a more permanent solution, consider using the Zotero citation manager, and taking the Libaries' Introduction to Zotero workshop.