One of the best Apps I have seen for FREE for group organization is Wunderlist. What is Wunderlist? Well, it is a simple to-do list (version 1.0) that you can share with anyone you would like, and set due dates and add notes. Ever since the upgrade to 2.0 you can have checklists for your checklists coupled with a notes section to meet most of our organizational needs.
Why is this app so great? First, it works on almost every major platform available from mobile devices, applications, or web apps. Furthermore, if you are managing a number of projects, or people with projects you can see and/or create a timeline with your team. Lastly, I personally love the fact that if someone is out sick before a deadline you can see how far along they have reached for their specific goals. The only bad part is if the lists have not saved/synced, which happens periodically on the apps, you will not have current information.
Personally the app has made me much more organized and I am working with my team to keep us all organized. There is the occasion that there needs to be a third layer nested for the to-do list, or a way to organize your lists without creating a lis for every piece of a larger list. However, it works with notes, just not something you can check off and have disappear. Maybe we will see an upgrade with version 3 that every sub list item will have its own note section?
Regardless of 2 minute shortcomings of the service it works incredibly well. I use it to plan out my blogs and keep the different topics organized for each day I write. It also sends me reminders when things need to be done, just make sure to set them before the time it is due! Do you use any type of organizational apps, and are they free?