Mindmeister is one of my favorite collaboration tools on the internet. It's incredibly easy to share maps with a group of people but also provides granular edit and view permissions to control it. We keep the Nerds on Draft podcast outlines and show schedules in Mindmeister.
Version 6.5 is out this week for iOS and it adds some nice enhancements. Notably for me, it adds split view support for the iPhone 6 Plus.
There's an assortment of iOS 9 enhancements like 3D Touch actions, peek and pop of maps, and Spotlight indexing. It's such a great service I wish more apps integrated with its API