Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Abstract - A secure, version-controlled hub for your design files
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Zeplin - Collaboration app for UI designers & frontend developers
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.
ActiveWords - Auto correct on steroids