Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Todoist - Todoist is a to-do list that helps you get organized, at work and in life.
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.
TickTick - TickTickis a cross-platform to-do list app & task manager helps you to get all things done and make life well organized.
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
Remember The Milk - Remember The Milk is a task and time management application for mobile devices.