Citavi: Citavi is a reference management tool that helps users organize their academic literature, manage citations, and collaborate with others. It also offers features for task management and knowledge organization.
ReadCube: ReadCube is a reference manager and PDF viewer that provides tools for organizing and annotating research papers. It includes features for discovering new literature and integrates with various databases.
Paperpile: This is a reference manager designed for Google Chrome. It allows users to organize and cite research papers directly within the browser. It also offers collaborative features for teams.
Mendeley: While Mendeley was mentioned in the question, it's worth noting that it continues to be a popular choice for reference management. It enables users to organize, annotate, and collaborate on research papers.
JabRef: JabRef is an open-source reference manager that uses BibTeX, which is a common bibliography file format in LaTeX. It's particularly suitable for users who work with LaTeX documents.
Colwiz: Colwiz is a reference management platform that not only helps with citation and reference organization but also offers collaboration tools, document annotation, and a personalized research library.
RefMe (Cite This For Me): RefMe was a popular citation tool that allowed users to scan book and journal barcodes to generate citations. It has now been integrated into the Cite This For Me platform.
Qiqqa: Qiqqa is a reference manager and document organizer that focuses on helping users discover and organize research articles. It includes features for annotation, tagging, and collaboration.