One Thing is described as 'Put your most important task or goal in the menu bar. Its presence there will help remind you without being annoying' and is a todo list manager in the office & productivity category. There are more than 100 alternatives to One Thing for a variety of platforms, including Web-based, Mac, iPhone, Android and Windows apps. The best One Thing alternative is Super Productivity, which is both free and Open Source. Other great apps like One Thing are Todoist, TickTick, Workflowy and Tasks.org.
92five app is self hosted (you can host it on your own server) project management web application. Projects, tasks, sub-tasks, time-sheets, to-dos, reports, timelines and much more are seamlessly managed in 92five app.
Tribe is the worlds first zero-adoption task manager. Use with anyone, on any device.
There's no download, no sign up, and no passwords. You can even use Tribe with others who don't use Tribe with you!
Canada
iGTD: Getting Things Done for MAC is a very useful MAC tool to get organised.
A free, simple todo list program for Windows. Fast as Notepad, supports subtasks, custom task orders and more. Works as a basic mind mapper as well.
Online GTD manager.
You can use it to manage your goals, projects and tasks, set next actions and contexts, use checklists, schedules and a calendar. A mobile version is available too.
United States
TODOWIZ is an app which will lend you a hand to accomplish the task that needs to be done on first priority. It lets you lighten up by keeping the important tasks on your finger tip that you can forget at any instant and helps you in fulfilling your task within deadlines.
Collaborate on projects, track time, manage expenses and invoice your customers. Available in the cloud, from any device!.
Australia
GTD-Free is personal TODO/action manager inspired by GTD (Getting Things Done) method by David Allen (see David Allen&Co. official site for more information). GTD-Free tries to be simple and easy to use management tool. GTD-Free is free open-source software.
Czechia
EU
The epic task management app that will keep you motivated with trophies, leveling up and comparing your workflow with others.
Task Office - existing GTD, to do lists, projects and contacts management apps. Designed to make business planning, scheduling and getting things done more efficient. Task Office makes your plans clear and achievable.
Actiontext is a very simple and basic universal app for managing your tasks. It uses the todo.txt file format. You can then synchronise the file with your cloud provider of choice.
United States
