Remember The Milk - Remember The Milk is a task and time management application for mobile devices.
Workflowy - A better way to organize your mind.
Planka - Planka is an open source project management software similar to Trello.
OmniOutliner - OmniOutliner is a writing app for collecting information, outlining ideas, adding structure to any sort of writing.
Dynalist - Dynalist is a web app that lets you break down and organize your thoughts in the format of lists.
Orgzly - Outliner for notes, tasks and to-dos