FusionDesk is described as 'helps you manage your projects and everyday tasks. Organizing your life and getting things done has never been easier' and is an app in the Office & Productivity category. There are eight alternatives to FusionDesk for a variety of platforms, including Mac, Windows, Linux, iPhone and BSD. The best alternative is Task Coach, which is both free and Open Source. Other great apps like FusionDesk are Tracks (Free, Open Source), The Hit List (Paid), ThinkingRock (Freemium) and Task List Guru (Free).
Tracks is a web-based application to help you implement David Allen’s Getting Things Done™ methodology. It was built using Ruby on Rails, and comes with a built-in webserver (WEBrick), so that you can run it on your own computer if you like.
TaskAgent is a simple to-do list manager that saves its lists as plain text files. While Dropbox syncing is optional, the benefit is that you can edit your lists from outside the app using your favorite text editor and then sync any changes back into the app.