BibMe features an "auto-fill" function that enables the user to locate a source by putting in the author or title If it finds a source, it adds information to the various fields and then the user can change or add additional information as they wish.
Citation Machine has free as well as paid subscription levels. Auto-fill and manual entry modes are available. Each citation must be individually saved to your document.
EasyBib offers premium editions provide note-taking options, data import and bibliography sharing.
KnightCite allows registered users to accumulate citations into bibliographies.
NoodleTools Express allows each citation to be individually saved to your document. A paid, subscription version is available that allows book data to be imported from WorldCat and that helps users to create bibliographies.
Scribbr.com - APA and Scribbr.com - MLA. Another set of free citation generators, these only for APA and MLA.
ZoteroBib enables users to create bibliographies right away from any device, without having to install software or register for an account. It is run by Zotero, the widely used bibliographic management tool. If you need to keep lists of sources or bibliographies or share them with other people, you should use the free downloadable application Zotero instead.