Mind mapping is an awesome activity for mobile devices, because it's inherently quick and requires very little typing. You can pull out your phone and tap up useful mind maps as you ride the train, wait to order lunch, or while you're standing in line at the airport. It's precisely this low-friction simplicity that makes mind maps such a powerful tool for productivity.
Here are a few of my favorite mind mapping apps for the most popular smartphone platforms.
There's no terrible shortage of mind mapping options for iOS, and some can set you back as much as $50. But for my money (which is about $0), it's hard to beat . The basic version is free for either iPad or iPhone, and as of this writing the manufacturer offers an upgrade to the full version (which supports both iPad and iPhone) for $2.99 as an in-app purchase.
SimpleMind+ is simplicity itself. Tap a little plus sign next to any node on your mind map to add a subnode. Tap in a label and then create more nodes. Tapping and dragging instantly rearranges your maps, and you can drop one node onto another to reassign it as a subnode. In all my years of mind mapping, I've yet to find a mind mapper as cheap, easy, and insanely useful as SimpleMind+ on the iPad. The iPhone version runs a close second.