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.