MindJet has long been one of our favourite mind mapping and collaboration tools, and has offered an iOS app for quite a while. There's now an Android equivalent, enabling quick access for existing MindJet sites.
As well as supporting a range of gestures for common tasks, you can sync MindJet files between your phone and your PC using Dropbox. Very handy if you want to update collaborative plans and maps on the go.
MindJet [Android Market]