Toggl - Toggl is an online time tracking tool. It features 1-click time tracking and helps you see where your time goes. Free and paid versions are available.

Todoist - Todoist is a to-do list that helps you get organized, at work and in life.

Hours - Boosting productivity through live, virtual co-working.

Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.

Futuramo Time Tracker - Futuramo Time Tracker is a time tracking solutions designed for freelancers and teams.

Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.