If you are looking for a mind mapping software, you may want to take a look at Joerg Mueller’s FreeMind, a mind-mapping software written in Java.
Although I am not really familiar with other mind-mapping software, I think Freemind is more than enough for simple concept maps such as the one shown below.
The sample mind map above is a draft mind map of the structure of Mathematics and Multimedia done in Freemind.
Freemind is a freeware – meaning it fully functional does not require any activation key, serial number or payment. Its latest version can be downloaded here.
Have fun mapping!