Inkscape - Inkscape is a free, open source professional vector graphics editor for Windows, Mac OS X and Linux.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Sketch - Professional digital design for Mac.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Affinity Designer - Professional creative software, exclusively for Mac.
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.