EssentialPIM - EssentialPIM is a free Personal Information Manager that keeps up with the times and lets you manage appointments, tasks, notes, contacts, password entries and email messages across multiple devices and cloud applications.
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
Todo.txt - Track your tasks and projects in a plain text file, todo.txt. A todo.
Pipefy - Pipefy is a process management software that empowers anyone to create and automate efficient workflows on their own without code.
Task Coach - Task Coach is a simple open source todo manager to keep track of personal tasks and todo lists.
Process Street - Create beautiful rich process documents in a simple to follow checklist format. Fast, free and incredibly simple to use.