Freemind is one of the most popular free mind mapping applications out there, and that’s mainly because it’s in Java and thus cross-platform (and because it’s a great app, of course). This software implements some of the major features that digital task lists have over paper task lists: retractable and expandable branches and hyperlinking between different branches make it easier to organize and easier to connect ideas.

bubble.us is a free web-based mind mapping application. You can sign up for an account in order to save your mind maps, but better still, they don’t force you to get an account to start creating. The interface could use some work to make it a truly usable application.

Semantik is a KDE Linux application for creating mind maps, though they can be viewed in different formats, such as a linear tree view with retractable and expandable branches.

MindMeister is another web app with varying account options; there’s a free account, and several commercial options. It has a fairly nice design and interface in comparison with many other mind mapping web apps that are available.

RecallPlus is commercial software with a lighter free edition. It combines the process of mind mapping with flash card memorization techniques, and is aimed at students who wish to take notes and then test themselves using them. RecallPlus is a Windows application.

Mindomo is another mind mapping web app with both a free account option and a commercial one. It allows you to share your mind maps with others, and also embed them into your web pages.

Mind42 is a totally free mind mapping web app and it is one of my favorites. The interface is a good one, and it has some excellent features such as easy navigation for large mind maps with zoom and birdview (and branch hiding, but that’s pretty standard these days), and the ability to attach notes and images to branches, which isn’t always allowed in “pure” mind mapping software. You can also link branches to other sites and see a preview when you rollover the link, which I think is probably the only appropriate use of those preview rollovers anywhere on the net.

Labyrinth is a very simple and basic mind mapping application for Linux and Windows.

Vym (View Your Mind) is an application for Mac OS X and various Linux distributions. There seems to be a Windows port, but it is accompanied by bug reports.

WiseMapping is another web app for mind mapping which requires no browser plug-ins at all, which is fantastic when you don’t know which computers you’ll be using in a given day. You can share, export and publish your mind maps from the app and there is no commercial account option; everything is free and unlimited.

PersonalBrain is a cross-platform application. It’s a commercial application, but a lighter free edition is on offer. I thought the integration of a calendar with events that you can add was a particularly cool addition and means you can brainstorm in not just the conceptual realm but cross over into the earlier stages of planning as well.