There are huge advantages to creating your mind maps with paper and pen. Although I am a technical person, pen and paper is simple to do, you don't worry about the computer crashing, you don't have any lag time, and you can get right down to work, and not have to worry about booking a lab or getting the computers. I find it simple to do when I don't have computers near. But remember that using some software and computers do get the students going, does make it fun, and interactive.
With that said here is a list of 5 free mind mapping applications and web services. You need to log into it for most of them, so be careful to not forget your user name and password.
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.
MindMeister is another web application 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.
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 its excellent 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.
WiseMapping is another web app for mind mapping which requires no browser plug-ins at all. You can share, export and publish your mind maps from the app and there is no commercial account option; everything is free and unlimited.