Asana is, without a doubt, one of the most popular Project Management online platforms. The system can automatically send notifications to users when new assignments are added or when the tasks are updated. Users can also keep track of task deadlines, or milestones.
[Top Ten] Best project management suite
This app tied with their online program is the best thing I have found for organizing myself with my GTD system. The most recent change of being able to add and edit subtasks was my biggest ask.
Tips for using the product
Best SOHO project management suite. Best pricing for small operations with very reasonable scalability costs, but the API and connected apps are the true gem. Highly recommended.