I needed a simple light weight todo manager where sharing is built into its heart. I already use powerful todo managers, project management tools, but I often need to collaborate with people outside of my team where they will be using altogether different todo tools. I then decided to build a simple todo tool that can be shared without asking user to sign in. https://donetogether.io
This can be used on top of existing tools. Focus is to mainly let users share a link to share the todo items.You can now group by assignee or due date. Hide columns if you don't need. Based on user feedback, I can build more features.