Qiqqa is by far the strongest solution for research and managing pdf's. Zotero, named as a comparison is weak as it does not allow pdf;s to be loaded into its interface - you need to use a pdf reader, which defeats its whole purpose. With Qiqqa documents in a library can be searched together. It has excellent maps of your libraries. It is not prefect, having a few glitches, but still is the only one of its kind.
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Process Street - Create beautiful rich process documents in a simple to follow checklist format. Fast, free and incredibly simple to use.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Pipefy - Pipefy is a process management software that empowers anyone to create and automate efficient workflows on their own without code.
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .